IGCSE/GCSE/O & A Level/IB/University Student Forum
Qualification => Subject Doubts => GCE AS & A2 Level => Sciences => Topic started by: elemis on October 03, 2010, 02:41:06 pm
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Please post all doubts here.
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what is the difference between electron acceptors and electron carriers?
And the difference between oxidative and photophosphorylation?
also any notes on the reactions of photosynthesis .
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what is the difference between electron acceptors and electron carriers?
And the difference between oxidative and photophosphorylation?
also any notes on the reactions of photosynthesis .
Sorry......won't be able to help you much now because am very busy.
Anyway try this and see if it helps..........ask any question and i'll attend to them later ;)
http://www.s-cool.co.uk/alevel/biology/respiration.html
http://www.biologymad.com/ -----> A2 Biology -----> Photosynthesis and Respiration
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Hi, does anyone know where I can get thorough notes on Malaria?
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Hi, does anyone know where I can get thorough notes on Malaria?
Try this for now :
http://www.biology-questions-and-answers.com/malaria.html
I'll keep on adding new sites as I find them ;)
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Explain why it has proved difficult to develop a vaccine for malaria. [4 marks]
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P. falciparum has demonstrated the capability, through the development of multiple drug-resistance parasites, of evolutionary change. The Plasmodium species has a very high rate of replication, much higher than that actually needed to ensure transmission in the parasite’s life cycle. This enables pharmaceutical treatments that are effective at reducing the reproduction rate, but not halting it, to exert a high selection pressure, thus favoring the development of resistance. The process of evolutionary change is one of the key considerations necessary when considering potential vaccine candidates. The development of resistance could cause a significant reduction in efficacy of any potential vaccine thus rendering useless a carefully developed and effective treatment.
From wikipedia : http://en.wikipedia.org/wiki/Malaria_vaccine#The_diversity_of_the_parasite (http://en.wikipedia.org/wiki/Malaria_vaccine#The_diversity_of_the_parasite)
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Okay, this is one the points I came across while going through the syllabus under 'Infectious Diseases':
Describe the roles of social, economic and biological factors in the prevention and control of cholera, malaria, TB and HIV/AIDS.
Can anyone explain what is meant by that and what do we need to know?
Thank you in advance!! :)
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Okay, this is one the points I came across while going through the syllabus under 'Infectious Diseases':
Describe the roles of social, economic and biological factors in the prevention and control of cholera, malaria, TB and HIV/AIDS.
Can anyone explain what is meant by that and what do we need to know?
Thank you in advance!! :)
These are not specifically found in the syllabus but you're supposed to know how and where these particular diseases are transmitted. This will help you to answer this question.
I'll take one by one, and i'll try to elaborate a bit.
1. Cholera
You should know that this disease is transmitted by fecal-oral route and the main mode of transmission is ingestion of contaminated water or food. It is most prevalent in places that lack adequate sanitary conditions.
Social factors : Sensitisation programmes must be launched through out the whole society so as to educate the inhabitants about the mode of transmission and cure of this disease in order that each one of them take precautions.
Economic : The states should provide money to afford the drugs or vaccine required to combat the disease.
Biological : The person should be in good health so that his immune system is effective against the disease.
2. Malaria
You must know the main preventive measures against malaria are the elimination of the vector mosquito, treatment of infected people, avoidance of the mosquito bite, information for travelers to endemic areas and the use of preventive medicines.
Social factors : Wear long sleeved shirts, take precautionary measures against mosquitoes.
Economic : Funds from the states.
Biological : Effective immune system.
3. Tuberculosis
You should be aware that tuberculosis is highly contagious, transmitted by air route through sneezes and coughs from a person with the active disease. Transmission is common between members of the same family or even in work environments. The disease today has treatment with efficient antibiotics. Generally, the patient receives three different drugs for several months until healing is complete. There are however some strains of multi-resistant TB-bacteria that emerged by mutation and natural selection due to the intense use of antibiotic drugs mainly in hospitals and treatment facilities; in these cases the treatment is more difficult.
Social factors : Again sensitisation programmes to isolate persons affected as the disease is highly contagious by air.
Economic : Funds should be provided by the governement.
Biological : Everyone should be in good health in order to contain e very effective immune system.
4. HIV/AIDS
You must be aware that HIV (human immunodeficiency virus) is supposed to be transmitted through blood, semen, vaginal secretions and maternal milk.
Social factors : Avoid from having various sex partners.
Economic : Condoms or pills should be readily available.
Biological : Do not risk the life of a baby.
As you can note, most of the factors resemble for most diseases but still you can opt for more appropriate ones according to the diseases' mode of transmission. ;)
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These are not specifically found in the syllabus but you're supposed to know how and where these particular diseases are transmitted. This will help you to answer this question.
I'll take one by one, and i'll try to elaborate a bit.
1. Cholera
You should know that this disease is transmitted by fecal-oral route and the main mode of transmission is ingestion of contaminated water or food. It is most prevalent in places that lack adequate sanitary conditions.
Social factors : Sensitisation programmes must be launched through out the whole society so as to educate the inhabitants about the mode of transmission and cure of this disease in order that each one of them take precautions.
Economic : The states should provide money to afford the drugs or vaccine required to combat the disease.
Biological : The person should be in good health so that his immune system is effective against the disease.
2. Malaria
You must know the main preventive measures against malaria are the elimination of the vector mosquito, treatment of infected people, avoidance of the mosquito bite, information for travelers to endemic areas and the use of preventive medicines.
Social factors : Wear long sleeved shirts, take precautionary measures against mosquitoes.
Economic : Funds from the states.
Biological : Effective immune system.
3. Tuberculosis
You should be aware that tuberculosis is highly contagious, transmitted by air route through sneezes and coughs from a person with the active disease. Transmission is common between members of the same family or even in work environments. The disease today has treatment with efficient antibiotics. Generally, the patient receives three different drugs for several months until healing is complete. There are however some strains of multi-resistant TB-bacteria that emerged by mutation and natural selection due to the intense use of antibiotic drugs mainly in hospitals and treatment facilities; in these cases the treatment is more difficult.
Social factors : Again sensitisation programmes to isolate persons affected as the disease is highly contagious by air.
Economic : Funds should be provided by the governement.
Biological : Everyone should be in good health in order to contain e very effective immune system.
4. HIV/AIDS
You must be aware that HIV (human immunodeficiency virus) is supposed to be transmitted through blood, semen, vaginal secretions and maternal milk.
Social factors : Avoid from having various sex partners.
Economic : Condoms or pills should be readily available.
Biological : Do not risk the life of a baby.
As you can note, most of the factors resemble for most diseases but still you can opt for more appropriate ones according to the diseases' mode of transmission. ;)
So this point in the syllabus just means that we suggest a social, economical and a biological preventive measure to combat these diseases?
Thank you VERY VERY MUCH for your help!! :D
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So this point in the syllabus just means that we suggest a social, economical and a biological preventive measure to combat these diseases?
Thank you VERY VERY MUCH for your help!! :D
Yupz.......you need to use all the theory you learnt on the specific disease to suggest a preventive measure.
Anytime :D
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1.Please explain why cell membranes are described as having "fluid mosaic" structure.
2. Explain, in terms of protein structure, how it is possible for each type of T cell receptor to
bind specifically to one type of antigen. [Ref: May/June 2002, Paper 2, Question 3 (b)]
Thanks in advance.
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1.Please explain why cell membranes are described as having "fluid mosaic" structure.
2. Explain, in terms of protein structure, how it is possible for each type of T cell receptor to
bind specifically to one type of antigen. [Ref: May/June 2002, Paper 2, Question 3 (b)]
Thanks in advance.
it is fluid because there is lateral diffusion of the fatty acid chains which make it looks like a fluid moving !
it is mosaic because there is protein molecules which has been scattered around the surface!
2)in each T cell receptor there is sequence of amino acids which bind to form a tertiary structure, this means that each T cell receptor has a different variable region. different receptors will bind with complementary antigens .
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it is fluid because there is lateral diffusion of the fatty acid chains which make it looks like a fluid moving !
it is mosaic because there is protein molecules which has been scattered around the surface!
2)in each T cell receptor there is sequence of amino acids which bind to form a tertiary structure, this means that each T cell receptor has a different variable region. different receptors will bind with complementary antigens .
Your answers are good but I would just like to add some precision, if you don't mind. ;)
1. Membranes are described as fluid mosaic structure since they consisit of proteins which are scattered among the phospholipid bi-layer giving rise to a mosaic appearance. Moreover the phospholipid within the bi-layer is always on the move rendering it fluid.
2. A T-cell contains a globular protein with a precise conformation showing tertiary structure. The amino acids are arranged in a specific sequence so that there is a variable region that allows only specific antigen with a complementary shape to bind.
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Thank You, DK!
Oh, I was doing a past paper this morning and there were questions on drug tolerance and caffeine and what not? I don't think that's in the 2010 CIE syllabus, right?
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Thank You, DK!
Oh, I was doing a past paper this morning and there were questions on drug tolerance and caffeine and what not? I don't think that's in the 2010 CIE syllabus, right?
Yeah it has been removed.
I guess you're doing old papers. ;D
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Yeah it has been removed.
I guess you're doing old papers. ;D
Yes, it's a 2003 paper. I'll just skip it. Thanks :)
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What role do the "papillary muscles" have in the initiation, coordination & the contraction of the heart.
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What role do the "papillary muscles" have in the initiation, coordination & the contraction of the heart.
Papillary muscle: Small muscles within the heart that anchor the heart valves.
Are you sure this is found in the syllabus ???
To tell the truth, i've never come across it. :-\
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I've never come across it either. But in some mark schemes they are some references to it so I was just wondering. Thank you, though. I'll look into it.
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I've never come across it either. But in some mark schemes they are some references to it so I was just wondering. Thank you, though. I'll look into it.
Ooh.........but i don't think we need to know about it. ;)
Just focus on those in the syllabus. :D
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Ooh.........but i don't think we need to know about it. ;)
Just focus on those in the syllabus. :D
Do we only have to do, which is there in the syllabus ? You never know !
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Do we only have to do, which is there in the syllabus ? You never know !
That's true. ;D
But it's highly improbable to get thing outside the syllabus. ;)
I said to focus on the syllabus since the majority if not all of the questions for the exams comes from there. :P
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That's true. ;D
But it's highly improbable to get thing outside the syllabus. ;)
I said to focus on the syllabus since the majority if not all of the questions for the exams comes from there. :P
That's right, take it as 99%, from the syllabus. When I sat CIE IGCSE Chemistry (0680), past May/June, there came a question about cyclo-alkene, of which topic was not present in syllabus, though answers were not related to that ! But for general, get doing extra things which are out of the syllabus, it will enable to catch questions comfortably.
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That's right, take it as 99%, from the syllabus. When I sat CIE IGCSE Chemistry (0680), past May/June, there came a question about cyclo-alkene, of which topic was not present in syllabus, though answers were not related to that ! But for general, get doing extra things which are out of the syllabus, it will enable to catch questions comfortably.
You should expanded your knowledge outside the syllabus during the whole year and not just before exams ;D
Anyways even if something outside the syllabus comes out, it's usually easy for it's either general knowledge or they give you some notes about it before asking the questions in the paper itself. ;)
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You should expanded your knowledge outside the syllabus during the whole year and not just before exams ;D
When did I tell, only before exams ? :P
Anyways even if something outside the syllabus comes out, it's usually easy for it's either general knowledge or they give you some notes about it before asking the questions in the paper itself. ;)
Same what I said...But in a different manner. :D
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When did I tell, only before exams ? :P
Same what I said...But in a different manner. :D
That was not specifically for you. Rather for Dania since both her and i are on the eve of exams. ;)
If you say so. :)
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How do companion cells load sucrose into sieve tube elements?
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How do companion cells load sucrose into sieve tube elements?
* Sieve tube elements: These are living, tubular cells that are connected end to end. The end cell walls have perforations in them to make sieve plates. The cytoplasm is present but in small amounts and in a layer next to the cell wall. It lacks a nucleus and most organelles so there is more space for solutes to move. The cell walls are made of cellulose so solutes can move laterally a well as vertically. Next to each sieve tube element is a companion cell.
* Companion cell: Since the sieve tube element lacks organelles, the companion cell with its nucleus, mitochondria, ribosomes, enzymes etc., controls the movement of solutes and provides ATP for active transport in the sieve tube element. Strands of cytoplasm called plasmodesmata connect the sieve tube element and companion cell.
* Parenchyma: Provides support through turgidity.
* Fibres: Provides support for the sieve tube elements.
http://en.wikipedia.org/wiki/Phloem
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How do companion cells load sucrose into sieve tube elements?
The sucrose id first loaded into the companion cell by active transport, using a protein molecule in the cell membrane as carrier or transporter. The latter pump out hydrogen ions actively. This creates a high concentration of H+ ions outside the companion cell.
Now the H+ ions diffuse back into the companion cell using a protein carrier down its concentration gradient. The latter move sucrose at the same time as the H+ ions. But the sucrose moves against its concentration gradient.
In other words, sucrose is being co-transported along with the H+ ions. The sucrose moves into the adjacent sieve tube elements through the plasmodesmata.
Hope it helps :)
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The sucrose id first loaded into the companion cell by active transport, using a protein molecule in the cell membrane as carrier or transporter. The latter pump out hydrogen ions actively. This creates a high concentration of H+ ions outside the companion cell.
Now the H+ ions diffuse back into the companion cell using a protein carrier down its concentration gradient. The latter move sucrose at the same time as the H+ ions. But the sucrose moves against its concentration gradient.
In other words, sucrose is being co-transported along with the H+ ions. The sucrose moves into the adjacent sieve tube elements through the plasmodesmata.
Hope it helps :)
Thank You! That's just what I need.
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How come no one has doubts about tomorrow's exam? I'm surprised.
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How come no one has doubts about tomorrow's exam? I'm surprised.
I think there are not many members sitting for Biology this year. :-[
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I think there are not many members sitting for Biology this year. :-[
Not many answer in the winter session.
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Not many answer in the winter session.
That's a good fact.
Candidates appearing in May/June sessions are far more than candidates appearing in October/November session.
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Does anyone have notes on this particular segment of Genetic Control?
Thanks in advance.
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Help! Anyone?
The answer is D.
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Does anyone have notes on this particular segment of Genetic Control?
Thanks in advance.
Sickle Cell Anaemia results from a substitution of one base which in turn transform the whole amino acid from the glutamic acid to valine. More precisely an adenine has been replaced by a thymine.
So the answer is A.
I do not have the specific notes but the application booklet for Chemistry (http://www.scribd.com/doc/19493970/A-Level-Chemistry-Application-Booklet-9701)(Page 39) is very helpful. Do take a look. ;)
Click here (http://www.ornl.gov/sci/techresources/Human_Genome/posters/chromosome/hbb.shtml) for more details about Sickle Cell Anaemia.
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Help! Anyone?
The answer is D.
The walls of both the alveolus and the capillary is one cell thick. Hence for gaseous exchange to occur the gas has to pass:
i) through the cell membrane of the one cell thick squamous epithelial cell of the alveoli so that it enters the cell.
ii) through the cell membrane of the same cell but in the opposite direction. The gas now leaves the cell, in other words it gets out of the alveoli.
iii) across the cell membrane of the one cell thick squamous epithelial cell of the capillary such that the gas enters the cell.
iv) across the cell membrane of the same cell but in opposite direction to get out of the cell and into the blood vessel.
v) lastly the gas needs to go through the cell membrane of the red blood cell for transport.
So in all, the gas has to pass across 5 cell membranes.
See the picture attached so that you may understand it better. ;)
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The walls of both the alveolus and the capillary is one cell thick. Hence for gaseous exchange to occur the gas has to pass:
i) through the cell membrane of the one cell thick squamous epithelial cell of the alveoli so that it enters the cell.
ii) through the cell membrane of the same cell but in the opposite direction. The gas now leaves the cell, in other words it gets out of the alveoli.
iii) across the cell membrane of the one cell thick squamous epithelial cell of the capillary such that the gas enters the cell.
iv) across the cell membrane of the same cell but in opposite direction to get out of the cell and into the blood vessel.
v) lastly the gas needs to go through the cell membrane of the red blood cell for transport.
So in all, the gas has to pass across 5 cell membranes.
See the picture attached so that you may understand it better. ;)
Thank you! Very helpful. Eid Mubarak!
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Thank you! Very helpful. Eid Mubarak!
Anytime :)
Eid Mubarak to you too. :D
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The answer to this is B. Can anyone explain why it is not A?
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The answer to this question is A. Why is it not B?
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The answer is D
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Please explain why the answer is D
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I think am a bit late. :-[
Am sorry I could not come online earlier but i was busy with Eid. :-\
However if you still want any clarifications concerning the questions below, do tell me. ;)
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I think am a bit late. :-[
Am sorry I could not come online earlier but i was busy with Eid. :-\
However if you still want any clarifications concerning the questions below, do tell me. ;)
It's alright. I managed to figure most of them out.
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It's alright. I managed to figure most of them out.
Ooh.....that's nice if you figured out by yourself. :D
Anyway hope you managed well in the exams. :)
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Quick question! :D
State 2 properties of water [other than boiling point and latent heat of evaporation] which make it suitable as a transport medium in the mammalian blood system.
I know 1, it's an excellent solvent for ions and polar molecules, but what can the second one be?
Thank you in advance!! :)
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Quick question! :D
State 2 properties of water [other than boiling point and latent heat of evaporation] which make it suitable as a transport medium in the mammalian blood system.
I know 1, it's an excellent solvent for ions and polar molecules, but what can the second one be?
Thank you in advance!! :)
The second one is the surface tension or strong cohesive force.
Water molecules tend to be attracted to each other and stick to each other by hydrogen bonding. So water molecules have high cohesion. This makes water in long tubes, such as in this case blood vessels, exists as a long continuous or unbroken column.
Hope it's clear :)
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The second one is the surface tension or strong cohesive force.
Water molecules tend to be attracted to each other and stick to each other by hydrogen bonding. So water molecules have high cohesion. This makes water in long tubes, such as in this case blood vessels, exists as a long continuous or unbroken column.
Hope it's clear :)
Yup, yup, very clear!! :D
Thanks a lot! :)
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Yup, yup, very clear!! :D
Thanks a lot! :)
Anytime mate :)
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Anytime mate :)
Hey man ! How are you ? ;)
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Hey man ! How are you ? ;)
Whats this?
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Whats this?
A biology doubt: an enquiry of Dead_King's bodily system. ::)
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A biology doubt: an enquiry of Dead_King's bodily system. ::)
If he's dead then, it should be POST MORTEM. :P
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Whats this?
Obituary, for Master_Key !
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If he's dead then, it should be POST MORTEM. :P
For you and the rest, he's still alive. ::)
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For you and the rest, he's still alive. ::)
At least some of you still have a good sense of observation. ;)
@ Ancestor : AM alright buddy and how are you doing? STill having problems in p1 or have you improved? :P
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At least some of you still have a good sense of observation. ;)
If that is irony, everybody will find you dead. :P ;)
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AM alright buddy and how are you doing? STill having problems in p1 or have you improved? :P
Yeah ! Doing good. Doubts still arise, when we move on with the chapters. :D
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Yeah ! Doing good. Doubts still arise, when we move on with the chapters. :D
I am always there to help you. :D
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If that is irony, everybody will find you dead. :P ;)
Hahaha...........my soul will continue to haunt you even then. :P
Yeah ! Doing good. Doubts still arise, when we move on with the chapters. :D
Yeah........that's normal. If doubts arise, it means you're progressing. ;)
We'll all be here to help you move on. :D
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Okay, mods. We are spamming now. :P
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question!
1) describe how aphids can be used to investigate the function of phloem. [3]
2) a) Describe fully the passage of water from the soil to the xylem tissue of plant roots. [4] --> ( I DONT NEED THE ANSWER TO THIS ONE)
b) Explain how this route is also used to carry nitrogen into the plant [4]
i just need the answer to 1 and 2b
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question!
1) describe how aphids can be used to investigate the function of phloem. [3]
2) a) Describe fully the passage of water from the soil to the xylem tissue of plant roots. [4] --> ( I DONT NEED THE ANSWER TO THIS ONE)
b) Explain how this route is also used to carry nitrogen into the plant [4]
i just need the answer to 1 and 2b
Check Your pm.
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Check Your pm.
Don't mind girl........but from now on it would be best that you post your explanations here.
This may be useful to other students as well.
And also if ever( I doubt that ;( ) you make mistakes, others can correct you. :)
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Don't mind girl........but from now on it would be best that you post your explanations here.
This may be useful to other students as well.
And also if ever( I doubt that ;( ) you make mistakes, others can correct you. :)
No,no no. I didn't know that he had posted his questions here. That person pm'ed me those questions. So, naturally I cleared his doubts via pm. Get it? :P
You are sweet. ;)
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No,no no. I didn't know that he had posted his questions here. That person pm'ed me those questions. So, naturally I cleared his doubts via pm. Get it? :P
You are sweet. ;)
Ooh.............now it's clear.
Well, it was the same thing for me before. But then I opted to post both questions and answers so that others can benefit from them as well ;)
Thanks for not misunderstanding me :)
But the king is not as sweet as his daughter. :D
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Ooh.............now it's clear.
Well, it was the same thing for me before. But then I opted to post both questions and answers so that others can benefit from them as well ;)
Thanks for not misunderstanding me :)
But the king is not as sweet as his daughter. :D
Yah, king. The daughter going to follow your footsteps ;)
No worries :D:D
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Kindly take this conversation towards the Halloween thread, AND NOT HERE ! :P
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need help with bio A2 paper 4 may/june 2003 question 2 (b)....wth does 'substrate level phosphorylation' means??!!:S
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A question, for the chapter Genetic Control, do we need to know the following?
1. Evidence that DNA not the protein in the chromosome is the genetic material
2. Evidence that DNA replicates by semi-conservative method
Thanks in advance! :)
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need help with bio A2 paper 4 may/june 2003 question 2 (b)....wth does 'substrate level phosphorylation' means??!!:S
SUBSTRATE-LEVEL PHOSPHORYLATION:The production of ATP by the direct transfer of a high-energy phosphate group from an intermediate substrate in a biochemical pathway to ADP
http://student.ccbcmd.edu/biotutorials/energy/fg2.html - click here for the picture.
Now you can figure out the answer for youself. ;)
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A question, for the chapter Genetic Control, do we need to know the following?
1. Evidence that DNA not the protein in the chromosome is the genetic material
2. Evidence that DNA replicates by semi-conservative method
Thanks in advance! :)
I dont think the first evidence is required but the second one about DNA replication and semi-conservative method is definitely needed.
I say, you check your syllabus. :)
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I dont think the first evidence is required but the second one about DNA replication and semi-conservative method is definitely needed.
I say, you check your syllabus. :)
Here's what the syllabus says:
(a) describe the structure of RNA and DNA and explain the importance of base pairing and hydrogen
bonding;
(b) explain how DNA replicates semi-conservatively during interphase;
(c) state that a gene is a sequence of nucleotides as part of a DNA molecule, which codes for a polypeptide;
(d) describe the way in which the nucleotide sequence codes for the amino acid sequence in a polypeptide
with reference to the nucleotide sequence for HbA (normal) and HbS (sickle cell) alleles of the gene for
the ?-haemoglobin polypeptide;
(e) describe how the information on DNA is used during transcription and translation to construct
polypeptides, including the role of messenger RNA (mRNA), transfer RNA (tRNA) and the ribosomes;
(f) explain that, as enzymes are proteins, their synthesis is controlled by DNA;
(g) use the knowledge gained in this section in new situations or to solve related problems.
It doesn't mention anything about it [evidence that DNA in the chromosome is the genetic material]
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Here's what the syllabus says:
(a) describe the structure of RNA and DNA and explain the importance of base pairing and hydrogen
bonding;
(b) explain how DNA replicates semi-conservatively during interphase;
(c) state that a gene is a sequence of nucleotides as part of a DNA molecule, which codes for a polypeptide;
(d) describe the way in which the nucleotide sequence codes for the amino acid sequence in a polypeptide
with reference to the nucleotide sequence for HbA (normal) and HbS (sickle cell) alleles of the gene for
the ?-haemoglobin polypeptide;
(e) describe how the information on DNA is used during transcription and translation to construct
polypeptides, including the role of messenger RNA (mRNA), transfer RNA (tRNA) and the ribosomes;
(f) explain that, as enzymes are proteins, their synthesis is controlled by DNA;
(g) use the knowledge gained in this section in new situations or to solve related problems.
It doesn't mention anything about it [evidence that DNA in the chromosome is the genetic material]
The evidence is not required. But you must only know that the DNA is actually the genetic material and not the protein.
The second one is essential as you must know the experiment using Nitrogen-14 and Nitrogen-15.
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The evidence is not required. But you must only know that the DNA is actually the genetic material and not the protein.
The second one is essential as you must know the experiment using Nitrogen-14 and Nitrogen-15.
Okay, thank you very much!! :)
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What the F**** does R-group mean, my stupid cie textbook keeps repeating this word in biological molecules without giving a definition of it, confusing me and not letting me understand anything!!! >:(
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What the F**** does R-group mean, my stupid cie textbook keeps repeating this word in biological molecules without giving a definition of it, confusing me and not letting me understand anything!!! >:(
R-Groups are a specific groups in amino acids and they vary greatly between amino acids. For eg. Glycine would have different R-Group than Valine. You do not need to know the names R-Groups at A levels but you may find it if you are interested.
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Question... Explain why cells that are produced as a result of mitosis are genetically identical. [3 marks]
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Question... Explain why cells that are produced as a result of mitosis are genetically identical. [3 marks]
during cell division, the DNA from the parent cell is taken as template. Both sister chromatids move to the opposite sides during metaphase and during interphase the chromatids replicate to form Chromosomes. since DNA is taken from a single parent cell they are genetically identical
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during cell division, the DNA from the parent cell is taken as template. Both sister chromatids move to the opposite sides during metaphase and during interphase the chromatids replicate to form Chromosomes. since DNA is taken from a single parent cell they are genetically identical
Thanks Ashish!! :)
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Okay, here's a couple of questions straight from the syllabus, I want to know what points should be mentioned under these questions:
1. Explain the importance of mitosis in growth, repair and asexual reproduction.
2. Explain the need for the production of genetically identical cells and fine control of replication.
3. Explain the need for meiosis prior to fertilization in sexual reproduction.
NOTE: They all belong to the chapter: Cell and Nuclear Division
Thanks a lot in advance! :)
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Okay, here's a couple of questions straight from the syllabus, I want to know what points should be mentioned under these questions:
1. Explain the importance of mitosis in growth, repair and asexual reproduction.
2. Explain the need for the production of genetically identical cells and fine control of replication.
3. Explain the need for meiosis prior to fertilization in sexual reproduction.
NOTE: They all belong to the chapter: Cell and Nuclear Division
Thanks a lot in advance! :)
1. Mitosis is important in these cases so as to replace dead cells with new identical ones which will carry out the same function as the others preceding it. Hence this is to ensure the survival of this particular species.
Example : (i) The body cells of a child undergoes mitosis for growth so that the child becomes bigger and have more developped organs which will be more efficient in their respective jobs.
2. Identical cells should be produced to ensure the survival of the respective species as well as the genes coding for it. If the cells are not identical the organism is going to be affected as the same genes will not be present and hence will not be able to carry out the wanted function.
3. Meiosis is required to half the number of chromosome in each gamete. This will ensure that upon fertilization the required number of chromosomes will be restored. In other words it prevents the number of chromosome to double each generation.
Example : (i) In man, we have 46 chromosome in each cell. Our body produces gamete with half the number of chromosome(23) such that at fertilization two gametes combine together to form one cell. Hence number of chromosome is restored. (23 + 23 = 46)
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1. Mitosis is important in these cases so as to replace dead cells with new identical ones which will carry out the same function as the others preceding it. Hence this is to ensure the survival of this particular species.
Example : (i) The body cells of a child undergoes mitosis for growth so that the child becomes bigger and have more developped organs which will be more efficient in their respective jobs.
2. Identical cells should be produced to ensure the survival of the respective species as well as the genes coding for it. If the cells are not identical the organism is going to be affected as the same genes will not be present and hence will not be able to carry out the wanted function.
3. Meiosis is required to half the number of chromosome in each gamete. This will ensure that upon fertilization the required number of chromosomes will be restored. In other words it prevents the number of chromosome to double each generation.
Example : (i) In man, we have 46 chromosome in each cell. Our body produces gamete with half the number of chromosome(23) such that at fertilization two gametes combine together to form one cell. Hence number of chromosome is restored. (23 + 23 = 46)
Finally someone replied!
THANK YOU VERY MUCH!! :D
I have another question:Can you please explain to me the experiment [evidence that DNA replicates by semi-conservative method]? I don't understand what this experiment is about and how is it conducted! :/
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Finally someone replied!
THANK YOU VERY MUCH!! :D
I have another question:Can you please explain to me the experiment [evidence that DNA replicates by semi-conservative method]? I don't understand what this experiment is about and how is it conducted! :/
Evidence for the semi-conservative replication of DNA.
In an experiment on e.coli(a bacteria) these were used to follow the DNA in the new cells every generation.
NOTE : Bacteria are used in this experiment since they replicate very rapidly causing this experiment not to last too long.(Generation time is about 50 minutes at 36oC)
The bacteria were grown in a nutrient medium containing the heavy isotope of Nitrogen-15. This replaced the normal Nitrogen-14 in the DNA. The bacteria labelled with N-15 contained the original or parental DNA. These bacteria were then transferred in a medium containing N-14 and allowed to grow.
Other similar bacteria were left for their DNA to replicate 2 or 3 times. The DNA was then extracted and centrifuged. The heavier the DNA, the closer to the bottom of the tube it settles. The DNA appeared as bands in the tubes as shown.
(http://www.mun.ca/biology/desmid/brian/BIOL2060/BIOL2060-19/1903.jpg)
As you can see only 50% of the original DNA is restored each generation. This is why it is called semi-conservative.
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Evidence for the semi-conservative replication of DNA.
In an experiment on e.coli(a bacteria) these were used to follow the DNA in the new cells every generation.
NOTE : Bacteria are used in this experiment since they replicate very rapidly causing this experiment not to last too long.(Generation time is about 50 minutes at 36oC)
The bacteria were grown in a nutrient medium containing the heavy isotope of Nitrogen-15. This replaced the normal Nitrogen-14 in the DNA. The bacteria labelled with N-15 contained the original or parental DNA. These bacteria were then transferred in a medium containing N-14 and allowed to grow.
Other similar bacteria were left for their DNA to replicate 2 or 3 times. The DNA was then extracted and centrifuged. The heavier the DNA, the closer to the bottom of the tube it settles. The DNA appeared as bands in the tubes as shown.
(http://www.mun.ca/biology/desmid/brian/BIOL2060/BIOL2060-19/1903.jpg)
As you can see only 50% of the original DNA is restored each generation. This is why it is called semi-conservative.
Thank you very very much! ;D
That was really simple, to the point and well-explained!! :)
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Thank you very very much! ;D
That was really simple, to the point and well-explained!! :)
Hehe.................anytime dude :D
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Do plant cells have lysosome structure? In wikipedia it says they dont, only animals do. But I came across the Multiple choice question in which the answer says that they infact do have lysosome structure. The past paper is 2010 cie 9700 qp_11 summer question number 4.
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th only structure present in animal cells that is absent in plant cells is the centriole
th only structuress present in plant cells that r absent in animal cells are:
-chloroplasts (photosynthesising cells only)
-cell walls
-plasmodesmata
-tonoplast and a large central vacuole
wat u came across in wiki may be diff, wrong, or xtra details tht rnt of requirement in ths syllabus
or u may hav misunderstood
nyways ths info is from my cie textbook so its trustworthy
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my doubt is:
in mj 04 ppr 4
Q 3(b) Explain three ways in which the cells of the proximal convoluted tubule are adapted for
selective reabsorption.
2 of th answers were:
tight junctions – prevent migration of membrane proteins / separate
tubule fluid ;
ref. to pincocytosis – protein uptake ;
i have no idea wat they're talkin bout n its not in my textbook so - ny1 has ny idea?
Q 5 Coat colour in cats is determined by a sex-linked gene with two alleles, black and orange.
When black cats are mated with orange cats, the female offspring are always tortoiseshell,
their coats show black and orange patches of various sizes, while the male offspring have
the same coat colour as their mothers.
(c) Suggest an explanation for the tortoiseshell coat in terms of the activity of the X
chromosomes.
th ans was:
X chromosome inactivated randomly early in development
wat does that mean? ::)
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my doubt is:
in mj 04 ppr 4
Q 3(b) Explain three ways in which the cells of the proximal convoluted tubule are adapted for
selective reabsorption.
2 of th answers were:
tight junctions – prevent migration of membrane proteins / separate
tubule fluid ;
ref. to pincocytosis – protein uptake ;
i have no idea wat they're talkin bout n its not in my textbook so - ny1 has ny idea?
for pt. 1 - tight junctions are an adaptation of the proximal convulated tubules. They (the junctions) prevent the passage of molecules and ions through the space between cells. So materials must actually enter the cells (by diffusion or active transport) in order to pass through the tissue. This pathway provides control over what substances are allowed through.
(http://images-mediawiki-sites.thefullwiki.org/07/3/3/1/03694351039901168.png)
2- you are supposed to refer to the pinocytosis process that takes place,
Small proteins which pass into the tubule during ultrafiltration are removed by pinocytosis at the base of the microvilli. They are enclosed in pinocytotic vesicles to which lysosomes are attached. Hydrolytic enzymes in the lysosomes digest the proteins to aminoacids which are either used by the tubule cells or passed on, by diffusion, to the blood capillaries.
Although, ::)
The proximal convoluted tubule cells are adapted for reabsorption as folloes:
i) large surfacearea due to microvilli and basal channels;
ii) numerous mitochondria;
iii) Closeness of blood capillaries.
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my doubt is:
in mj 04 ppr 4
Q 5 Coat colour in cats is determined by a sex-linked gene with two alleles, black and orange.
When black cats are mated with orange cats, the female offspring are always tortoiseshell,
their coats show black and orange patches of various sizes, while the male offspring have
the same coat colour as their mothers.
(c) Suggest an explanation for the tortoiseshell coat in terms of the activity of the X
chromosomes.
th ans was:
X chromosome inactivated randomly early in developmentwat does that mean? ::)
Each cell in a female's body contains two X chromosomes, but one is 'inactive' or 'turned-off' through a normal process called X-inactivation.Because X-inactivation is random, in normal females the X chromosome inherited from the mother is active in some cells, and the X chromosome inherited from the father is active in other cells.
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Question, how do you prepare for a biology practical exam? [Paper 3]
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Each cell in a female's body contains two X chromosomes, but one is 'inactive' or 'turned-off' through a normal process called X-inactivation.Because X-inactivation is random, in normal females the X chromosome inherited from the mother is active in some cells, and the X chromosome inherited from the father is active in other cells.
thank u v much both xplanations wer very helpful
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Question, how do you prepare for a biology practical exam? [Paper 3]
You performed the practicals once in the classes right?
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You performed the practicals once in the classes right?
Yup! But I'm asking what do I do before going for my test, at home, like the day before.
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Yup! But I'm asking what do I do before going for my test, at home, like the day before.
Practice drawing cells-very thin cell walls if it's a plant cell and the more variety of cell structures you draw the better prepared you will be to draw any organelles that you may see on the day which you may recognize from practice.
And also you will be much more likely to label correctly.
- And revise food tests, make sure you know the procedure well and the results of the experiments well.
- Practise Graphs
- Go through your lab manual
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thank u v much both xplanations wer very helpful
My pleasure, Sue. ;)
And sorry for the late reply.
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Practice drawing cells-very thin cell walls if it's a plant cell and the more variety of cell structures you draw the better prepared you will be to draw any organelles that you may see on the day which you may recognize from practice.
And also you will be much more likely to label correctly.
- And revise food tests, make sure you know the procedure well and the results of the experiments well.
- Practise Graphs
- Go through your lab manual
Thank you! :)
What's a lab manual? :/
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Thank you! :)
What's a lab manual? :/
It's that book you use in the lab. :P :D
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It's that book you use in the lab. :P :D
LOL :D Okay! :)
Thanks!
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(http://)
4 Fig. 4.1 is a diagram drawn from a photomicrograph of an animal cell undergoing meiosis.
(a) Identify the stage of meiosis shown in Fig. 4.1.
...[2]
figure attached
th answer is : metaphase 2
from which angle does this look like metaphase 2?????
ps- i cant attach the image ! :(
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(http://)
4 Fig. 4.1 is a diagram drawn from a photomicrograph of an animal cell undergoing meiosis.
(a) Identify the stage of meiosis shown in Fig. 4.1.
...[2]
figure attached
th answer is : metaphase 2
from which angle does this look like metaphase 2?????
ps- i cant attach the image ! :(
try uploading figure 4.1 again, because all I see is a cross where the pictromicrograph should be. :-X
Meiosis 1 - http://botit.botany.wisc.edu/images/130/Meiosis/Lilium_microsporogenesis/Meiosis_1.jpg
Meiosis 2 - http://faculty.irsc.edu/FACULTY/TFischer/images/meiosis%202.jpg
http://botit.botany.wisc.edu/images/130/Meiosis/Lilium_microsporogenesis/Metaphase_II_MC_.low.jpg
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Got it attached!
:D
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Got it attached!
:D
This looks like Telophase 1.
the second picture?
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This looks like Telophase 1.
the second picture?
According to the mark scheme it's metaphase 2 and I really don't know how!
and this is the only picture related to the question!
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According to the mark scheme it's metaphase 2 and I really don't know how!
and this is the only picture related to the question!
Those chromosomes are alighned at the equator.
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A2 : section B nov 2008 it says Describe and explain, using an example, the process of artificial selection.
ok so then in th m.s. 2 points wer like:
-background genes ;
-loss of hybrid vigour / increase in homozygosity / ref. inbreeding depression
does ny1 no wat these r?
+ if ny1 hs some notes on all ths speciation, artificial selection things pls do attach - my text book hs become useless :'(
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A2 : section B nov 2008 it says Describe and explain, using an example, the process of artificial selection.
ok so then in th m.s. 2 points wer like:
-background genes ;
-loss of hybrid vigour / increase in homozygosity / ref. inbreeding depression
does ny1 no wat these r?
+ if ny1 hs some notes on all ths speciation, artificial selection things pls do attach - my text book hs become useless :'(
- Hybrid vigour (heterosis/outerbreeding enhancement) describes the strength of different characteristics in hybrids; the possiblity of obtaining a genetically superior individual by combining the virtues of its parents.
Homozygosity: The state of possessing two identical forms of a particular gene, one inherited from each parent.For example, a girl who is homozygous for cystic fibrosis (CF) received the CF gene from both of her parents and therefore she has CF.
Interbreeding depression - is the reduced fitness in a population as a result of breeding of related individuals. It results in more recessive deliterious traits manifesting themselves. More homozygous deleterious genes the offspring may have, the more unfit the offspringproduced.
Check out these links.
Speciations - http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/S/Speciation.html
http://www.dr-evans.com/advancedbiology/evolution.html
http://www.sparknotes.com/biology/evolution/naturalselection/section3.rhtml
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thanks alot! :D
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thanks alot! :D
I dint realize I've quoted your question twice! :D
Welcome!
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another question - a small one
(b) Explain the role of gibberellins in the germination of wheat or barley.
among all th points was :
13 gibberellin produced by embryo plant ;
14 passes to aleurone layer ;
15 switches on / activation, transcription enzyme genes / AW ;
16 storage proteins broken down to amino acids ;
17 stimulates synthesis / release of amylase ;
18 amylase diffuses / moves into endosperm ;
now points 15 16 17 - which enzyme is being transcripted? is it like a protease cuz in th nxt step they go like proteins to aminos? & then amylase is synthesised because of the aminos?
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another question - a small one
(b) Explain the role of gibberellins in the germination of wheat or barley.
among all th points was :
13 gibberellin produced by embryo plant ;
14 passes to aleurone layer ;
15 switches on / activation, transcription enzyme genes / AW ;
16 storage proteins broken down to amino acids ;
17 stimulates synthesis / release of amylase ;
18 amylase diffuses / moves into endosperm ;
now points 15 16 17 - which enzyme is being transcripted? is it like a protease cuz in th nxt step they go like proteins to aminos? & then amylase is synthesised because of the aminos?
The outerlayers of endosperm contains proteins which is the source of amino acids for protien synthesis.
Germination is triggered by soaking the seed in water. After imbibing water the embryo secrets gibberellin which diffuses into the aleurone layer, stimulating synthesis of several enzymes including alpha amylase. These enzymes catalyse the breakdown of food reserve in the endosperm, and the products of digestion diffuse to the embryo, where they are used in growth.
Take a look at the images to understand better. :)
http://4e.plantphys.net/images/ch20/wt2002c_s.jpg
http://forums.mycotopia.net/attachments/testing-formating/30670d1154787401-seed-germination-lab-seedgerm.gif
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thanx again :)
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thanx again :)
My pleasure. :)
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its question 5 e i from nov 2009
its attached
the ans is th asterisk is marked at day 9 - why??????
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its question 5 e i from nov 2009
its attached
the ans is th asterisk is marked at day 9 - why??????
In fig 5.1 on day 9, the concentration of LH is very low. And the purpose of antagonist to LH secretion is to decrease the secretion of LH.
And so, the antagonist to LH will be given on day 9th.
This will prevent ovulation.
Tell me, if you dont understand. ;)
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but isnt the conc of LH on day 9 already low? why do we need 2 decrease it further in order 2 prevent ovulation?
(sorry 4 asking 10 days later)
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but isnt the conc of LH on day 9 already low? why do we need 2 decrease it further in order 2 prevent ovulation?
(sorry 4 asking 10 days later)
the concentration is LH is low on day 9 because of the treatment of antagonist of LH.
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For CIE A2 (or AS) level students:
I was just going thru the marking schemes of Biology papers and what confuses me is that there are 4 points mentioned for a 2 mark question or sometimes 8 points mentioned for a 4-mark question. Now unlike chemistry or physics, sometimes they don't mention explicitly in their schemes that where all or some are needed so I am just wondering which one is the case? In chemistry and physics, as a general rule, you get one number for one point.
Because 8 points for a 4 point question seem quite a lot to me. They are basically all that you could write in response to that question which is usually not the case as students gets full points for writing different (but correct answers) that may or may not match the scheme.
So would anyone kindly clarify the schemes for biology? For example Question 5(c) for May/June 2010 Paper 42.
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Out of the 8 points given you could write any 4 points. As long as you have written 4 points you would get your 4 marks.
Its the same for the 2 mark question.
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hi
can anyone give some tips in paper 5 for bio. Its very tough.thanks in advance
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hi
can anyone give some tips in paper 5 for bio. Its very tough.thanks in advance
Paper 5 requires practical thinking and practise. Do the past papers and you'll be fine.
Good luck. :)
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Paper 5 requires practical thinking and practise. Do the past papers and you'll be fine.
Good luck. :)
thanks. i really hope so...............
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Can someone please draw for me the plan diagrams that you would draw for the stages of mitosis when you're viewing them from a slide?
Thanks in advance! :)
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Can someone please draw for me the plan diagrams that you would draw for the stages of mitosis when you're viewing them from a slide?
Thanks in advance! :)
Draw the diagrams in exactly the same way you view it in the microscope.
The cytoplasm... and then the stages of mitosis.
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Draw the diagrams in exactly the same way you view it in the microscope.
The cytoplasm... and then the stages of mitosis.
That's the thing, I want to know how would you represent prophase, interphase, telophase in a plan diagram.
Thanks anyways! :)
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can anyone explain MJ 2002 P1 Q21 please?
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can anyone explain MJ 2002 P1 Q21 please?
Can you post the question? I cant find that paper.
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I have a doubt in the circulatory system.
The heart's cardiac muscles are described as myogenic, right?
Myogenic means that the contraction of the muscles is initiated from the muscles itself and the term neurogenic means that the contraction of the muscles is initated from the nerves.
When we learnt the cardiac cycle, it was the SAN that received the impulse from the Cardiac Acceleratory/Inhibitory Center in the medulla oblongata of the brain which was transmitted through the vagus nerve till it reachs the SAN which sends the impulse to the walls of the atria to contract and the impulse is transmitted to the apex of the heart through the Purkinje fibres and the muscles contract, so as you see, it's contraction initiated by an impulse, so why is the cardiac muscle described as myogenic!
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I have a doubt in the circulatory system.
The heart's cardiac muscles are described as myogenic, right?
Myogenic means that the contraction of the muscles is initiated from the muscles itself and the term neurogenic means that the contraction of the muscles is initated from the nerves.
When we learnt the cardiac cycle, it was the SAN that received the impulse from the Cardiac Acceleratory/Inhibitory Center in the medulla oblongata of the brain which was transmitted through the vagus nerve till it reachs the SAN which sends the impulse to the walls of the atria to contract and the impulse is transmitted to the apex of the heart through the Purkinje fibres and the muscles contract, so as you see, it's contraction initiated by an impulse, so why is the cardiac muscle described as myogenic!
AM sorry I can't summarize it for you now since am pretty busy myselft......................but do read the first part of this ;)
http://www.tutorvista.com/biology/physiology-of-the-human-heart
It is said that SAN is only partly controlled by sympathetic nerve. ;)
Do not read everything koz I don't think it is in the \A-lvel syllabus :P
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AM sorry I can't summarize it for you now since am pretty busy myselft......................but do read the first part of this ;)
http://www.tutorvista.com/biology/physiology-of-the-human-heart
It is said that SAN is only partly controlled by sympathetic nerve. ;)
Do not read everything koz I don't think it is in the \A-lvel syllabus :P
Thanks a lot, actually my teacher had taught us the entire thing, it's pretty interesting.
& I got it, the contraction of the cardiac muscle starts from SAN which is a muscle by itself.
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Guys, someone make my day and reply with a 'no' to this question, do we need to know the structure of the trachea, cartilage and smooth muscle with all those amazing terms 'mucosa', 'chondrocytes', 'lacuna', 'cell nest', 'squamous pnemocyte type (1)' and 'secretory pnemocyte type (2)'?
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MJ 2008 P1 Q21 & Q24,can anyone help me in this type of question,ive perfected everything else other than this pain,and is glycogen a poymer of alpha glucose or what?
Thanks
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Guys, someone make my day and reply with a 'no' to this question, do we need to know the structure of the trachea, cartilage and smooth muscle with all those amazing terms 'mucosa', 'chondrocytes', 'lacuna', 'cell nest', 'squamous pnemocyte type (1)' and 'secretory pnemocyte type (2)'?
No, you don't have to.
Did I make your day? ::) :P
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MJ 2008 P1 Q21 & Q24,can anyone help me in this type of question,ive perfected everything else other than this pain,and is glycogen a poymer of alpha glucose or what?
Thanks
Glycogen is a monomer of alpha glucose, yes.
You know about the complementary bases of DNA, right? Adenine binds with Thymine and Cytosine binds with Guanine. (This is for DNA.) The complementary base for Adenine in RNA is Uracil. So accordingly;
Q 21 - B. If you introduce a thymine molecule in the position 'B' the triplet in DNA will be ATC. The complimentary codon of ATC in RNA will be UAG (the stop codon).
Q 22 - D. The mRNA codons for the sickle cell heamoglobin has been listed. Now, you have to find the complementary codon of the tRNA that doesnot help in the making of sickle cell. The codon for tRNA D will be ACG - this is not listed as one of the anti-codons which forms sickle cell heamoglobin.
I hope you get it. ;)
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No, you don't have to.
Did I make your day? ::) :P
YOU DIIIIIIIIIIIIIIIIIIIID!! BIG TIME!! :D :D :D :D :D
So, in the chapter gas exchange, we're supposed to know:
-the adaptations of the alveoli as gaseous exchange surface
-inhalation and exhalation [what happens during them]
-definitions like tidal volume, residual volume, vital capacity, etc.
-tobacco smoke and COPD and the effect of nicotine, CO, etc.
that's it?
& what about 'epidemiological evidence' whether in this chapter or in the cardiovascular diseases, do we need to know that as well, as in would we be asked to provide such evidence?
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YOU DIIIIIIIIIIIIIIIIIIIID!! BIG TIME!! :D :D :D :D :D
So, in the chapter gas exchange, we're supposed to know:
-the adaptations of the alveoli as gaseous exchange surface
-inhalation and exhalation [what happens during them]
-definitions like tidal volume, residual volume, vital capacity, etc.
-tobacco smoke and COPD and the effect of nicotine, CO, etc.
that's it?
Yup, that's pretty much it. ;)
& what about 'epidemiological evidence' whether in this chapter or in the cardiovascular diseases, do we need to know that as well, as in would we be asked to provide such evidence?
Yes, you do need to know about that. You wont be asked to provide evidence but I think, the questions will as such the evidences will be provided and questions will be asked based on them. Get my point?
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Yup, that's pretty much it. ;)
& what about 'epidemiological evidence' whether in this chapter or in the cardiovascular diseases, do we need to know that as well, as in would we be asked to provide such evidence?
Yes, you do need to know about that. You wont be asked to provide evidence but I think, the questions will as such the evidences will be provided and questions will be asked based on them. Get my point?
So we basically just go through them to have an idea and in the exam it's all about applying your concepts according to the situation presented, right?
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So we basically just go through them to have an idea and in the exam it's all about applying your concepts according to the situation presented, right?
Right. (Y)
And don't worry. Tbh, Biology theory papers are easy enough. ;)
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MJ 2008 P1 Q21 & Q24,can anyone help me in this type of question,ive perfected everything else other than this pain,and is glycogen a poymer of alpha glucose or what?
Thanks
MJ 2008 P1 Q21 & Q24 please,and thanks for the ans Amelia :)
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MJ 2008 P1 Q21 & Q24 please,and thanks for the ans Amelia :)
I edited my above post, Hush. Check it out, I've answered. :)
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Right. (Y)
And don't worry. Tbh, Biology theory papers are easy enough. ;)
Really? I hope to 'feel' that soon, I'm currently studying the entire syllabus throughly first and then I'll move on to past papers! :)
Thank you very much! :D
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Thanks alot Amelia +rep ;),sorry for the trouble but can you explain the second question again ;(
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Anyone can help with the diagram in MJ 2005 Q4. part c please?
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Anyone can help with the diagram in MJ 2005 Q4. part c please?
which paper?
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Paper 2
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Paper 2
theres no 4c! maybe u r asking from the a-level pastpaper? Im studying IGCSE
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yeah its AS why else would i post it here?
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yeah its AS why else would i post it here?
oh so i cnt help sry ;D
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yeah its AS why else would i post it here?
Hey hush!
It involves the hydration of C-N that's amide bond.
One product is a -COOH.
Another is an -NH2.
Note:- C-N bond is broken so separate the molecule from here. R-COOH AND H2N-R.
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Thanks alot Amelia +rep ;),sorry for the trouble but can you explain the second question again ;(
The mRNA forms the polypeptide chain and the tRNA molecules bring forth the anti-codons required to make the polypeptide chain.
The tRNA A is CAU - it's complementry codon in mRNA will be GUA (aminoacid Valine is present in the formation of sickle cell)
The tRNA B is CUU - it's complementry codon in mRNA will be GAA (aminoacid glutamine is present in the formation of sickle cell)
The tRNA C is UGA - complementry codon in mRNA is ACU (thronine is also present in the formation of amino acid of sickle cell)
But the tRNA D is UGC and its codon in mRNA is ACG (therefore, this amino acid is 'not' present in the formation of sickle cell)
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Thanks alot Amelia & Master for your explanation :D
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Thanks alot Amelia & Master for your explanation :D
Keep posting. :P
Good Luck, mate.
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Thanks alot Amelia & Master for your explanation :D
ANYTIME dude.
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hey
need help with Q 24 and 30 M/J 2006 P1
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hey
need help with Q 24 and 30 M/J 2006 P1
Q24
u have 20% of cytocine in DNA so this will be transcripted to 20% guanine in mRNA
U have 20 % of cytocine in DNA so there would be 20 % guanine (its complimantory base pair) which will be transcripted to guanine (20% in mRNA)
u r left with :- 100-(20+20) = 60%
this 60% would includes both Ucracil and ADenine bot in equal proprtion as they are complimentory base pai
so half of 60 % would be ucracil
60%/2 = 30%
Q30
i know that co2 concentration would shift X to Y but dont know how cn this be dne by increasing pH
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Q24
u have 20% of cytocine in DNA so this will be transcripted to 20% guanine in mRNA
U have 20 % of cytocine in DNA so there would be 20 % guanine (its complimantory base pair) which will be transcripted to guanine (20% in mRNA)
u r left with :- 100-(20+20) = 60%
this 60% would includes both Ucracil and ADenine bot in equal proprtion as they are complimentory base pai
so half of 60 % would be ucracil
60%/2 = 30%
Q30
i know that co2 concentration would shift X to Y but dont know how cn this be dne by increasing pH
Thanks for the answer. I understand the first one but for Q30 I think you answered a wrong question. I'm talking about the one with the atrio-ventricular and the semi-lunar valves..
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can someone please draw an outline of how you would draw a table for question 1b(i) m/j 2007 31 without the values...just the column headings.
Here is the link: http://www.xtremepapers.me/CIE/International%20A%20And%20AS%20Level/9700%20-%20Biology/9700_s07_qp_31.pdf (http://www.xtremepapers.me/CIE/International%20A%20And%20AS%20Level/9700%20-%20Biology/9700_s07_qp_31.pdf)
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can someone please draw an outline of how you would draw a table for question 1b(i) m/j 2007 31 without the values...just the column headings.
Here is the link: http://www.xtremepapers.me/CIE/International%20A%20And%20AS%20Level/9700%20-%20Biology/9700_s07_qp_31.pdf (http://www.xtremepapers.me/CIE/International%20A%20And%20AS%20Level/9700%20-%20Biology/9700_s07_qp_31.pdf)
place 2 cm3 of distilled water in a test-tube.
• add 2 cm3 of starch solution.
• add 0.5 cm3 of amylase and start timing.
• after five minutes add four drops of iodine solution and shake gently.
So we got
Note:- Keep the time for the experiment constant as for example 5 minutes for Amylase to work on Starch.
VOLUME OF STARCH ADDED
VOLUME OF AMYLASE ADDED
CONCENTRATION OF LEAD NITRATE ADDED
TIME TAKEN FOR STARCH TEST TO OBTAIN RESULT / TIME TAKEN FOR BLUE-BLACK COLOUR TO DEVELOP
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Is the concentration of lead nitrate meant to be in % ?
Is it going to be something like this: volume of lead nitrate
---------------------- x 100
volume of (lead nitrate + water)
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Is the concentration of lead nitrate meant to be in % ?
Is it going to be something like this: volume of lead nitrate
---------------------- x 100
volume of (lead nitrate + water)
If the question has it in % then take it in %.
For eg. 1% CuSo4 is 1% of mass of solution not necessarily volume.
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Method of measuring curvature?
Specimen Paper 5-2007, Q2: mentioned in the marking scheme.
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how do we measure the rate at which the amylase break down into starch ?
In my boook its says that : To measure the rate of this reaction is to measure the rate at which the starch disappears from the reaction mixture
This can be done by taking samples at known times n doing the iodine test. starch forms blue-black colour with this solution using a colorimeter to measure the intensity of the blue-black colour obtained using this yu can measure the starch remaining...... so yes i was wondering as the amount of starch disappear means that reaction is proceeding rght so lighter the intensity of the colour in the colorimeter the faster the reaction
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Guys, what's the correct steps for calibrating the eyepiece graticule?
Let's say that 2 eyepiece divisions correspond to 65 stage micrometer divisions and that one division on the stage micrometer is equal to 0.01 mm, how would you calibrate it?
& if you want to find the actual length of something that you measured that turned out to have 3.5 eyepiece graticule divisions, what would your answer be?
I've got 2 ways to calculate, I get 2 answers that when rounded off to 2 s.f. are the same, but when you calculate the size of a specimen, with the 2 values, I get 2 different answers!
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how do we measure the rate at which the amylase break down into starch ?
In my boook its says that : To measure the rate of this reaction is to measure the rate at which the starch disappears from the reaction mixture
This can be done by taking samples at known times n doing the iodine test. starch forms blue-black colour with this solution using a colorimeter to measure the intensity of the blue-black colour obtained using this yu can measure the starch remaining...... so yes i was wondering as the amount of starch disappear means that reaction is proceeding rght so lighter the intensity of the colour in the colorimeter the faster the reaction
you can use benedict's test to find the rate at which reducing sugar is formed from starch
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Guys, what's the correct steps for calibrating the eyepiece graticule?
Let's say that 2 eyepiece divisions correspond to 65 stage micrometer divisions and that one division on the stage micrometer is equal to 0.01 mm, how would you calibrate it?
& if you want to find the actual length of something that you measured that turned out to have 3.5 eyepiece graticule divisions, what would your answer be?
I've got 2 ways to calculate, I get 2 answers that when rounded off to 2 s.f. are the same, but when you calculate the size of a specimen, with the 2 values, I get 2 different answers!
2 = 65
2 Eyepiece divisions = 0.65 mm
3*0.65 / 2 = 1.1375 mm.
Thats the calculation.
I think you made some mistake though i gave the calculation, its the method. Now when you xamine microscope always the eyepiece divisions are large in number compared to stage micrometer divisions like
47 Eyepiece graticule divisions (arbitrary units) = 1 Stage micrometer because stage micrometer is always magnified and it always corresponds to a large number of Eyepiece graticule divisions. Check it!
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2 = 65
2 Eyepiece divisions = 0.65 mm
3*0.65 / 2 = 1.1375 mm.
Thats the calculation.
I think you made some mistake though i gave the calculation, its the method. Now when you xamine microscope always the eyepiece divisions are large in number compared to stage micrometer divisions like
47 Eyepiece graticule divisions (arbitrary units) = 1 Stage micrometer because stage micrometer is always magnified and it always corresponds to a large number of Eyepiece graticule divisions. Check it!
But I remember during my lab classes that the eyepiece graticule we used had values from 0-10, so how can you say there's '47' eyepiece graticule divisions?
The stage micrometer is the one that's in the 'slide', right, that one usually has divisions from 0-100!
I'm sorry for the confusion! :s
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& one more question, how do you draw a plan diagram for this?
http://fsweb.bainbridge.edu/acunningham/BIOL2112/imgBIOL2112/LungSlide-Normal-01.jpg
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& one more question, how do you draw a plan diagram for this?
http://fsweb.bainbridge.edu/acunningham/BIOL2112/imgBIOL2112/LungSlide-Normal-01.jpg
AHHHA PRESIDENT i Got ya :o 8)
Well anyways I thnk yu need to draw the plan digram for the vessel in cardovascular systen Lke Teh capillaries n vein n arties ... ;D
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Can sumone pplz show the slide of a caradiac muscle n describe it i google it i cant find
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AHHHA PRESIDENT i Got ya :o 8)
Well anyways I thnk yu need to draw the plan digram for the vessel in cardovascular systen Lke Teh capillaries n vein n arties ... ;D
Okay, I don't get what do you mean by your first line.
& That was a normal lung by the way, can you please draw a plan diagram for it if you can?
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:-[ i thought u were some one from my skoool
Ok r u telling me draw a plan diagram of lung ???
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:-[ i thought u were some one from my skoool
Ok r u telling me draw a plan diagram of lung ???
Of what you see in that photo I shared.
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But I remember during my lab classes that the eyepiece graticule we used had values from 0-10, so how can you say there's '47' eyepiece graticule divisions?
The stage micrometer is the one that's in the 'slide', right, that one usually has divisions from 0-100!
I'm sorry for the confusion! :s
You might be using a different eyepiece graticule. Eyepiece graticules change from models to models. Well you might have one with 10. We might have one with 100. :)
The stage micrometer is the one that's in the 'slide', right, that one usually has divisions from 0-100! Not really. It may change but CIE will provide something for examination.
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You might be using a different eyepiece graticule. Eyepiece graticules change from models to models. Well you might have one with 10. We might have one with 100. :)
The stage micrometer is the one that's in the 'slide', right, that one usually has divisions from 0-100! Not really. It may change but CIE will provide something for examination.
Alright, thank you! :)
& can you please check my previous question here about the plan diagram of the lungs?
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Alright, thank you! :)
& can you please check my previous question here about the plan diagram of the lungs?
Plan diagram is drawing only OUTLINES AND NO CELLS. You need to draw the walls of alveoli and other walls visible there.
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Plan diagram is drawing only OUTLINES AND NO CELLS. You need to draw the walls of alveoli and other walls visible there.
Okay, thanks! :)
Can you please give me a draft answer [like what points should be mentioned] for answer 1b in June 2001? The MS is not available online! :s
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Okay, thanks! :)
Can you please give me a draft answer [like what points should be mentioned] for answer 1b in June 2001? The MS is not available online! :s
Which paper exactly?
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Which paper exactly?
Paper 3 - the practical one!
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can someone please explain how to work out q 2a(ii) in O/N 2008 31
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can someone please explain how to work out q 2a(ii) in O/N 2008 31
it's simple
the eyepiece gratiule is not callibrated but is jus marked with equal gaps
but the stage micrometer is callibrated according to the magnifiaction,
in the first blank write the number of eyepiece graticule units and the ans would be near 8.0
then for the 2nd and 3rd blank look at fig 2.3, look at the fifth division from zero on the figure circle and the 4.5 in the smaller scale, they both exactly superimpose
and so
as the fig say that Each division on the stage micrometer
scale is 0.1 mm so te size of one unit on eye piece grativule would be 4.5/5 *0.1mm
you have lumen of eightof 8 unit of eyepiece graticule unit so multiple egiht with 4.5/5*0.1
u get ur ans in mm
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Explain
What the procedure of serial dilution ?
AASAP
Thanz
http://www.freeexampapers.com/past_papers.php?l=Past_Papers%2FA+Level%2FBiology%2FCIE%2F2009+Jun/
Question 1 (a) (ii)
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Explain
What the procedure of serial dilution ?
AASAP
Thanz
http://www.freeexampapers.com/past_papers.php?l=Past_Papers%2FA+Level%2FBiology%2FCIE%2F2009+Jun/
Question 1 (a) (ii)
- weigh 20 gm of the given glucose in the balance.
- Pour 50 cm3of warm water in a beaker.
- Add the 20 gm glucose in the beaker.
- Stir the mixture
- Then add more 50cm3, to make it up to 100cm3.
Refer to serial dilution - http://toolboxes.flexiblelearning.net.au/demosites/series3/308/laboratory/studynotes/SNHowToPerfrmSrlDilutn.htm
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Are we meant to keep the solution in water bath when testing for the break down of starch by amylase?
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Are we meant to keep the solution in water bath when testing for the break down of starch by amylase?
Yes if testing at different temperatures.
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Biology Paper 5, specimen paper:
Q2. How to measure the curvature???
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How to do the Q1 bi and ii?
My answer wasn't matching the one for the marking scheme! :S
-
Doubt attached in the marking scheme!
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Doubt in Q2 b(iii)
-
2 doubts attached!
-
Doubts attached!
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Doubt: my answer was opposite to mark scheme (marked) :S please explain!
-
Doubt attached!
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Doubt attached! Please explain Point 11!
-
Doubt attached!
Why can't we use a water bath to maintain the temperature? ? ? :S
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What role does oxygen play in oxidative phosphorylation?
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2 doubts attached!
b iii) its jus that if you look at the 2 means -> 0 .156 +/- .001 and 0.197 +/-.013 then you'll see that the upper limit for the first mean (0.156+0.001=0.157) and the lower limit for the second mean (0.197-0.013=0.184) dont overlap - there is a difference between them - so bottom line is there is a difference between the means since their ranges dont overlap ;)
biv) you have to look at the method by which they obtained the means in th table at the begining of th ques. Now they said for each pH, th samples wer monitored at 1 hour intervals for 20hours - so each mean has a degrees of freedom of 19 - now they compared the mean at two pHs so 19x2=38 - if u still dont get it call me
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Doubts attached!
counting the number of cells on the grid under view gives th no. of cells per 0.04mm2 (since its th area of the grid) If less than half of the cell is in the grid, its not counted. The area 0.04 is multiplied by the depth 0.1mm to give the volume of the grid. this gives 0.004mm3. Now jus count the number of cells under view and divide by the volume (which is identical to multiplying by 250 cuz 1/0.004 = 250) to find the no. of cells per mm3 - mention doing repeats n etc...
next part - it was mentioned in the begining tht th original number of cells was 3thousand. in the table where the mean is - the column heading is thousands of cells per mm3 of culture - so ur mean of 6.2 is actually 6.2 thousand --- now for calculating th percentage increase just follow wat they said takinf th final number as ur mean value and the original number as 3 - thts it
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Doubt: my answer was opposite to mark scheme (marked) :S please explain!
see the thing is ur supposed 2 draw conclusions from the graph wether ther is a relationship between the fragmentation index and the conc of this CB-153 thing - now between 60 and 120 u can see a large increase and no overlap of error bars - which supports th theory that th inc in CB causes damage to the DNA - but wen u look at 120 - onwards there is a lot of overlap - so ther cod be no relationship - as in you cant really see anymore wether an increase in CB really causes damage
jus rethink this and look at th answer again - ull b sure 2 get it ;)
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Doubt attached!
organism 1 has the antibody for antigen X so one line shows up in front of it - organism 2 has th antibody for both antigens so u c 2 lines ( a line forms because a ppt appears due 2 th antigen meeting its antibody.
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Doubt attached! Please explain Point 11!
see to ensure reliability you have 2 tell them: carry out the experiment in the same area when u repeat it - cuz like other areas myt have some more pollen in the air - its jus 2 produce more reliable results
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Doubt attached!
Why can't we use a water bath to maintain the temperature? ? ? :S
i think its cuz it myt affect th humidity which decreases th rate of transpiration and affects the rate of movement up the stem ;)
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What role does oxygen play in oxidative phosphorylation?
oxygen acts as the final electron acceptor in the ETC - its necessary cuz it being can combine with the electron which has passed through th ETC and it accepts it (i guess otherwise it wod have no wer else 2 go this lone electron) so wat u need 2 no is without a final electron acceptor those energy changes down ur ETC wont work... there are a few markin scheme answers about this - get 2 no them...
By the way good job attachin ur doubts - saves alot of trouble from jus naming them
and ill answer the specimen 5 questions after monday (cuz i hav an xam n i havent done th ppr) hope thts ok!
cya on wednesday ;)
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JazakAllah Khair for your help, sister!
:D
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oxygen acts as the final electron acceptor in the ETC - its necessary cuz it being can combine with the electron which has passed through th ETC and it accepts it (i guess otherwise it wod have no wer else 2 go this lone electron) so wat u need 2 no is without a final electron acceptor those energy changes down ur ETC wont work... there are a few markin scheme answers about this - get 2 no them...
By the way good job attachin ur doubts - saves alot of trouble from jus naming them
and ill answer the specimen 5 questions after monday (cuz i hav an xam n i havent done th ppr) hope thts ok!
cya on wednesday ;)
It's alright! I'll call you up on Monday (insha Allah) if I have any doubts remaining- hopefully not!
Thank you once again for your help and time!
*I could hug you right now* :D
All the best for Chem! ;)
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Using a respirometer for finding effect of temperature for rate of respiration. Do we use soda lime (KOH) in the apparatus?
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question!
-Some people have a rare disease caused by a single change in the DNA nucleotide
sequence of the gene coding for lysozyme. The change leads to the formation of an
insoluble protein that has a different structure to the normal soluble lysozyme molecule.
Suggest how a change in the gene can lead to the differences observed between the
normal lysozyme and the changed lysozyme.
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Some one please help me with this! I don't have the official answer for this. I want to compare my answer with whoever helps me! =)
1-Bowman's Capsule/Renal Capsule
2-Glomerulus
3-Afferent Arteriole
4-Efferent Arteriole
5-Proximal Convoluted Tubule
6-Distal Convoluted Tubule
7-Collecting Duct
8-Loop of Henle
9-Vasa Recta
PLEASE CORRECT ME IF I AM WRONG!
-
(http://www.anselm.edu/homepage/jpitocch/genbio/nephron.JPG)
Here.
-
Can someone please explain this?
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(http://www.anselm.edu/homepage/jpitocch/genbio/nephron.JPG)
Here.
Thank you.
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Just a quick question, are we supposed to know the 4 different classes of antibodies [IgG, IgM, IgA, IgE] and their functions, sites of action, number of antigen binding sites and their relative molecular mass?
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Just a quick question, are we supposed to know the 4 different classes of antibodies [IgG, IgM, IgA, IgE] and their functions, sites of action, number of antigen binding sites and their relative molecular mass?
As such you just need to know that which is heavier for your safety. I haven't seen any paper which asks for such detailed description but you may remember it.
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Can someone please explain this?
No one? :S
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As such you just need to know that which is heavier for your safety. I haven't seen any paper which asks for such detailed description but you may remember it.
mmmm, there's alot that comes under 'study to be on the safe side for bio'! :s
Thank you very much though! :)
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mmmm, there's alot that comes under 'study to be on the safe side for bio'! :s
Thank you very much though! :)
Study to be on safe side. :P
Welcome ;)
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Just a couple of questions here,
Specimen paper 2001, Q3 a iii) - What's the answer?
Specimen paper 2001, Q4 is about genetic engineering, is that part of our syllabus?
Specimen paper 2001, Q3 b) - What's the answer?
Can anyone please send me the link to the MS of this paper?
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Explain the relationship between action spectrum and absorption spectrum.
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How do we know what type of inhibitor the chemical/substance that is added is?
Example: Q3 a iii) on this paper: http://www.xtremepapers.me/CIE/International%20A%20And%20AS%20Level/9700%20-%20Biology/9700_w10_qp_23.pdf
How do we know it's a non-competitive/irreversible inhibitor?
& someone please answer my previous questions:
Just a couple of questions here,
Specimen paper 2001, Q3 a iii) - What's the answer?
Specimen paper 2001, Q4 is about genetic engineering, is that part of our syllabus?
Specimen paper 2001, Q3 b) - What's the answer?
Can anyone please send me the link to the MS of this paper?
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How do we know what type of inhibitor the chemical/substance that is added is?
Example: Q3 a iii) on this paper: http://www.xtremepapers.me/CIE/International%20A%20And%20AS%20Level/9700%20-%20Biology/9700_w10_qp_23.pdf
How do we know it's a non-competitive/irreversible inhibitor?
& someone please answer my previous questions:
Just a couple of questions here,
Specimen paper 2001, Q3 a iii) - What's the answer?
Specimen paper 2001, Q4 is about genetic engineering, is that part of our syllabus?
Specimen paper 2001, Q3 b) - What's the answer?
Can anyone please send me the link to the MS of this paper?
Cu2+ ions are not the shape of sucrose so it is non-competitive.
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How do we know what type of inhibitor the chemical/substance that is added is?
Example: Q3 a iii) on this paper: http://www.xtremepapers.me/CIE/International%20A%20And%20AS%20Level/9700%20-%20Biology/9700_w10_qp_23.pdf
How do we know it's a non-competitive/irreversible inhibitor?
Like MK said, Cu+ ions are not the shape of the sucrose so they do not attach themselves in the active-sites of the enzymes but elsewhere in the enzyme molecule. They alter the shape of the enzyme in such a way that the active site can no longer accomodate the substrate. As the substrate & inhibitor molecules attach on different parts of the enzyme, they are not competing for the same sites (non-competivite). Also, metal ions break the disulphide bonds(that help maintain the shape of the enzyme molecule). This causes the enzyme molecule's structure to be irreversibly altered.
& someone please answer my previous questions:
Attach the questions please. :-\
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Explain the relationship between action spectrum and absorption spectrum.
An action spectrum is a graph showing the effectiveness of different wavelengths of light in stimulating the process being investigated. An absorption spectrum is a graph of the relative amounts of lights absorbed at different wavelengths by a pigment.
An action spectrum for photosynthesis is shown together with an absorption spectrum for the combined photosynthetic pigments.
(http://5e.plantphys.net/images/ch07/wt0701c.png) http://5e.plantphys.net/images/ch07/wt0701c.png
NOte the close similarity, which indicates that the pigments, cholorophylls in particular, are those responsible for absorption of light in photosynthesis.
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An action spectrum is a graph showing the effectiveness of different wavelengths of light in stimulating the process being investigated. An absorption spectrum is a graph of the relative amounts of lights absorbed at different wavelengths by a pigment.
An action spectrum for photosynthesis is shown together with an absorption spectrum for the combined photosynthetic pigments.
(http://5e.plantphys.net/images/ch07/wt0701c.png) http://5e.plantphys.net/images/ch07/wt0701c.png
NOte the close similarity, which indicates that the pigments, cholorophylls in particular, are those responsible for absorption of light in photosynthesis.
Thanks for your help. :)
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Explain why sickle cell anaemia is common in areas where malaria is endemic ?
0/n 6b p2
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Like MK said, Cu+ ions are not the shape of the sucrose so they do not attach themselves in the active-sites of the enzymes but elsewhere in the enzyme molecule. They alter the shape of the enzyme in such a way that the active site can no longer accomodate the substrate. As the substrate & inhibitor molecules attach on different parts of the enzyme, they are not competing for the same sites (non-competivite). Also, metal ions break the disulphide bonds(that help maintain the shape of the enzyme molecule). This causes the enzyme molecule's structure to be irreversibly altered.
Attach the questions please. :-\
What I meant is how would you know the shape of Cu ions, like why can't you say that it competes with the substrate and it becomes a competitive inhibitor?
I don't have a soft copy of the paper, so I'll type the questions for you in a while, or probably scan it for you.
Thanks Amelia and Master_Key :)
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I've attached the paper here in 2 parts.
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Biology Paper 5, specimen paper:
Q2. How to measure the curvature???
ok so as promised, Vampire-love - here r th answers 2 ur previous posts ;)
first for ths one u dont really need 2 bother about that - there are lots of other points you could write - but anyways you can always say to use a protractor to measure th curvature - just state it like that u dont need to include so much detail :-\
1bi and ii) the marking scheme is messed up - they can always be rong u no!
here is wat u shod get: mean for tissue A = 56 sA= 2.357 and SM= 0.75
mean for B = 123.3 sB=2.312 and SM= 0.73
the bar chart will become hard 2 draw with its error bars once you get these values - but dont worry its their fault :p its just a specimen paper...
thats it - good luck 2moro ;) cya!
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ok so as promised, Vampire-love - here r th answers 2 ur previous posts ;)
first for ths one u dont really need 2 bother about that - there are lots of other points you could write - but anyways you can always say to use a protractor to measure th curvature - just state it like that u dont need to include so much detail :-\
1bi and ii) the marking scheme is messed up - they can always be rong u no!
here is wat u shod get: mean for tissue A = 56 sA= 2.357 and SM= 0.75
mean for B = 123.3 sB=2.312 and SM= 0.73
the bar chart will become hard 2 draw with its error bars once you get these values - but dont worry its their fault :p its just a specimen paper...
thats it - good luck 2moro ;) cya!
Thank you my dear! ! ! :D See you after 8 hours! :D
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Any risk assessed by using hydrogen carbonate solutions?
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What I meant is how would you know the shape of Cu ions, like why can't you say that it competes with the substrate and it becomes a competitive inhibitor?
Because it's sort of a fact that metal ions do not attach themselves to the active site of the enzyme. Hence, they are not 'competing' with the substrates. They are simply changing the shape of the enzyme. This (http://www.chemguide.co.uk/organicprops/aminoacids/enzymes3.html) will explain better.
Specimen paper 2001, Q3 a iii) - What's the answer?
I'm not sure about this question. Maybe, because protease works at a range of pH and it is difficult or inaccurate to deduce the range for the graph.
Specimen paper 2001, Q4 is about genetic engineering, is that part of our syllabus?
Yes, it's included. It'll be easy to solve this question, once you learn the concept.
Specimen paper 2001, Q3 b) - What's the answer?
Optimum temperature for the enzyme protease to work upon.
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Explain why sickle cell anaemia is common in areas where malaria is endemic ?
0/n 6b p2
Sickle-cell anaemia provides protection against malaria. The parasite cannot survive in the blood cells of a person who has got the heterogenous sickle cell genes.
Individuals carrying just one copy of the sickle mutation (inherited from either the father or mother) were known not to develop sickle cell anemia, leading rather normal lives. However, it was found that these same individuals, said to carry the sickle cell trait, were in fact highly protected against malaria, thus explaining the high prevalence of this mutation in geographical areas where malaria is endemic.
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Because it's sort of a fact that metal ions do not attach themselves to the active site of the enzyme. Hence, they are not 'competing' with the substrates. They are simply changing the shape of the enzyme. This (http://www.chemguide.co.uk/organicprops/aminoacids/enzymes3.html) will explain better.
I'm not sure about this question. Maybe, because protease works at a range of pH and it is difficult or inaccurate to deduce the range for the graph.
Yes, it's included. It'll be easy to solve this question, once you learn the concept.
Optimum temperature for the enzyme protease to work upon.
THANK YOU! :D
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Sickle-cell anaemia provides protection against malaria. The parasite cannot survive in the blood cells of a person who has got the heterogenous sickle cell genes.
Individuals carrying just one copy of the sickle mutation (inherited from either the father or mother) were known not to develop sickle cell anemia, leading rather normal lives. However, it was found that these same individuals, said to carry the sickle cell trait, were in fact highly protected against malaria, thus explaining the high prevalence of this mutation in geographical areas where malaria is endemic.
malarial parasite cnt acctually enter the RBC which r not biconcav
it cn attack only healthy RBC
SICKLE CEELL ANEMIA cuses deformation of RBC and it is HEREDITRCAL desease cused by Genetic DISOORDER
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Explain how crossing over leads to variation.
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Explain how crossing over leads to variation.
Crossing over changes some of the chromatids sequence. This results in different alleles expressed. So variation is seen.
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Crossing over changes some of the chromatids sequence. This results in different alleles expressed. So variation is seen.
Thanks. :)
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Role of plasmodesmata.
-
major role while water diffuses by SYMPLOPLAST PATHWAY
-
List some ethical reasons against IVF.
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List some ethical reasons against IVF.
what is IVF?
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what is IVF?
In-Vitro Fertilisation.
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many reliogion dont allow artificial birth
in IVF many time sprem r donated by sme unknow person so it becomes very diicult to find the real father of the son, when concerd with property and inheritance of capital
not accepted by sme society
many eggs r fertilised and only one out of them is used so this state that the rest human being (although just a cell) r being killed
i dont remembr any more of the....
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many reliogion dont allow artificial birth
in IVF many time sprem r donated by sme unknow person so it becomes very diicult to find the real father of the son, when concerd with property and inheritance of capital
not accepted by sme society
many eggs r fertilised and only one out of them is used so this state that the rest human being (although just a cell) r being killed
i dont remembr any more of the....
Thanks! ;) I'll elaborate more on those points. :)
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Specimen Paper 4, Q8 part (a) and (ci). For part a, I attached the MS answer but it makes no sense and part ci how do we do the calculation?
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I must've posted this before also but I am sorry, I still don't get it. How do we know it's Metaphase II?
-
How to do this Question?
-
From Oct/Nov '05
*Q1b
*Q2a- don't know how to do (getting stuck in between) & we get the chi square value as 1.8 and so answers to part d & e doesn't make much sense! :S
-
What on earth is a Minor Process/Foot? ???
-
Oct/Nov '08 Q8.
-
Q7ci
-
Please explain how to do Q5e!
-
Please explain how to do Q5e!
srry i m still n AS
-
srry i m still n AS
It's ok. :(
-
How to show synaptic knob in a myelinated sensory neurone? !
-
How to show synaptic knob in a myelinated sensory neurone? !
You can show the synapse at the transmitting end to intermediate neuron. Use a cleft in diagram to show it.
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Specimen Paper 4, Q8 part (a) and (ci). For part a, I attached the MS answer but it makes no sense and part ci how do we do the calculation?
my dear you are looking at the wrong marking scheme hehehehehe - here ive attached th right one - hope it clears things up ;)
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How to do this Question?
attached
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From Oct/Nov '05
*Q1b
look at the cycle in your text book, how after citrate, you go directly to a 6C intermediate - now after this, th 6C intermediate changes into a 5C sugar after being decarboxylated and dehydrogenated by NAD - the next step also there is decarboxyyy and dehydrogennaa. also, they have included not only th krebs cycle but the link reaction as well - remeber there is decarboxylation and dehydrogenation in th link reaction so, you'll put in th labels at three sites (attached). dehydrogenation is the removal of the hydrogen which here is done by NAD or FAD - so there are two more sites for dehydrogenation also... hope im clear...
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From Oct/Nov '05
*Q1b
*Q2a- don't know how to do (getting stuck in between) & we get the chi square value as 1.8 and so answers to part d & e doesn't make much sense! :S
so they've described the offsprings and from the appearance of the numbers you should no this 9:3:3:1 ratio is typical of two heterozygous-for-both-alleles type of parent - ive attached th working.. incomplete though
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Thank youuuuuuuuu, Sue T!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! <3
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From Oct/Nov '05
*Q2a- don't know how to do (getting stuck in between) & we get the chi square value as 1.8 and so answers to part d & e doesn't make much sense! :S
you got a value of 1.8 and in the chi table the values increase as the probability decreases - so - 1.8 lies at a probabilty greater than 0.05 ryt? then once u've established that you say tht the fact that th probability is grater than .05 then, the diffferences between the observed and expected values are insig and only due 2 chance - so the expected ratio of offspring 9:3:3:1 is observed and the assumptions u made (as in th parents being heterozygous) are correct ;)
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is there any need to go through t test, standard error and standard deviation for paper 4? cuz i haven't seen any questions from there in paper 4's yet. just thought i'd ask and double check.... :D
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OctNov06- number 2.. How is it done? ._. It seems to be so confusing!
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OctNov06- number 2.. How is it done? ._. It seems to be so confusing!
Which paper?
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IF YOU ARE DOING PAPER 4 (which I'll assume you are :p)
Anyways, I hope you see this- poisonedrose!
See the attachments! (I hope it's clear enough)
Explanation: As the question mentions, a cross between two dogs with copper hair tips always produces copper hair tips- meaning it must be homozygous recessive. As only one allele is being expressed.
A cross with two black dogs will produce off springs SOME with red hair tip & copper hair tip (some black off springs too). Meaning both the parents must be heterozygous.
I am sorry if my explanation isn't clear enough! :$
Re-read the question and I am sure you'll get it!
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:) you're amazing. Thank you so much.
After reading the question.. 6?7? times, with your explanation, I finally got it.
Time to hit the hay however.
Good luck all of you guys here :)
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Welcome! ;) Good luck!
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I have couple to ask For p1
What substances dissolve phospholipids
http://www.xtremepapers.me/CIE/International%20A%20And%20AS%20Level/9700%20-%20Biology/9700_w07_qp_1.pdf
Question 14 ,22 ,29 ,35
THANKS
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35 - Antibiotics cure bacterial diseases. Cholera and Tuberculosis. So, ans is A.
29 - Systolic blood pressure represents the maximum pressure exerted when the heart contracts. So, its C.
22) - complementary base pairing along some of its length
- an area that can attach to a ribosome
-a site to which a specific amino acid attaches
All describing tRNA. Ans, D.
14) - A. http://ccnmtl.columbia.edu/projects/biology/lecture7/images/ncinhgra.jpg
- Lipids can be dissolved with the use of organic solvents like alcohol.
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Can anyone please explain to me how do you go about Q22, the answer is B.
http://www.xtremepapers.me/CIE/International%20A%20And%20AS%20Level/9700%20-%20Biology/9700_w10_qp_11.pdf
& explanation for Q 17, 30 and 34 of this paper:
http://www.xtremepapers.me/CIE/International%20A%20And%20AS%20Level/9700%20-%20Biology/9700_s06_qp_1.pdf
as well as Q14 & 18 in June 2002 and Q26 & 32 in Nov 2002 [I can't find online links for both these papers, sorry]
Thanks! :)
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22) if u would look closely then % of nitrogenous base of A--D and B--C would be (almost) equal so this tells that A--D is a pair and B--C is another pair,
now look at Uracil when the uracils is present , C is nil then this shows that C is Thymine and as C is paired with B, B is Adanine
17) i m confused too but i think the A is correct as C and D sound senseless as water would entre cell so the water potentail of cell would increas (more +Ve) and water poteintial of solution decreases (more -ve) and the solute potential would also increase with water potential as
water potenial in plant cell = pressue potenital + solute potenial
and thus to increase water potential (as the cylinder are diipped in solution with lessesr conce. (more water potenital) the pressure potenitial and solute potential should be increased
HOPE i m not confusing u
30)
i think it has to be C (not sure)
as
the ans = (2-1)+(4-3)
34)
HIV/AIDS caused by virus, malaria by parasites and TB by Bacteria
so , virus dont respire and dnot have ribosomes, Parasites dont have surface membrane
so the ans is D
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22) if u would look closely then % of nitrogenous base of A--D and B--C would be (almost) equal so this tells that A--D is a pair and B--C is another pair,
now look at Uracil when the uracils is present , C is nil then this shows that C is Thymine and as C is paired with B, B is Adanine
17) i m confused too but i think the A is correct as C and D sound senseless as water would entre cell so the water potentail of cell would increas (more +Ve) and water poteintial of solution decreases (more -ve) and the solute potential would also increase with water potential as
water potenial in plant cell = pressue potenital + solute potenial
and thus to increase water potential (as the cylinder are diipped in solution with lessesr conce. (more water potenital) the pressure potenitial and solute potential should be increased
HOPE i m not confusing u
30)
i think it has to be C (not sure)
as
the ans = (2-1)+(4-3)
34)
HIV/AIDS caused by virus, malaria by parasites and TB by Bacteria
so , virus dont respire and dnot have ribosomes, Parasites dont have surface membrane
so the ans is D
Thank you, and your answers are right By the way! xD
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Yeh toh hamara kaam hein
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Can someone please explain the following?
November 2006 - Q11 and 19
June 2005 - Q5
November 2004 - Q27, 30 and 38
June 2004 - Q32
November 2002 - Q26 and 32
June 2002 - Q 14 and 18
Thank you! :D
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Can someone please explain the following?
November 2006 - Q11 and 19
June 2005 - Q5
November 2004 - Q27, 30 and 38
June 2004 - Q32
November 2002 - Q26 and 32
June 2002 - Q 14 and 18
Thank you! :D
November 2006
Q11-ans A
Hot Water is less denser Than Cold water Cuz of that It brings the Dissolved nutrients to the surface
And Also water is called A universal Solvent it dissolve most of the Substance
Q29-ans B
Air pressure is much less as the alttitude increase thus the Partial pressure of Oxygen Decrease
Saturation of haemoglobin will be less (%)
So Less oxygen carried around the body Which Cause sickness
June 2005 - Q5- ans C
0.25 mol dm^–3 sucrose solution in order to maintain the organelles osmotic integrity. The respiratory substrate used by mitochondria is glucose, not sucrose.
November 2004 - Q38
Used for growth + used for other life process + respiratory heat losses( But this hw yu get the answers but i m nt sure y)
June 2004 - Q32 ans D
diffuses through the squamous epithelial cells of the alveolar wall and then through the endothelial cells of
the capillary wall or they failed to understand that the oxygen crosses two cell surface membranes as it
diffuses into and then out of each cell. The fifth membrane is, the surface of the red blood cell.
June 2002 -
Q 14 ans B
The substrate concentration is high the And the is nt free for the enzymes so the substrate molecules Wait for their turn
Q18 Ans C
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A farmer wants to encourage the beneficial bacterial reactions involved in the nitrogen cycle in wheat fields. How can he do this?
A adding artificial nitrate fertiliser
B draining waterlogged fields
C growing the same crop every year
D irrigating fields
Okay, now I think the most likely answer is B. Draining waterlogged soils will discourage the reaction of denitrifying bacteria in the soil. Dentrifying bacteria reduce soil fertility by converting nitrates to atmospheric nitrogen. Not so beneficial for the wheat fields.
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A farmer wants to encourage the beneficial bacterial reactions involved in the nitrogen cycle in wheat fields. How can he do this?
A adding artificial nitrate fertiliser
B draining waterlogged fields
C growing the same crop every year
D irrigating fields
Is the answer D
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November 2006
Q11-ans A
Hot Water is less denser Than Cold water Cuz of that It brings the Dissolved nutrients to the surface
And Also water is called A universal Solvent it dissolve most of the Substance
Q29-ans B
Air pressure is much less as the alttitude increase thus the Partial pressure of Oxygen Decrease
Saturation of haemoglobin will be less (%)
So Less oxygen carried around the body Which Cause sickness
June 2005 - Q5- ans C
0.25 mol dm^–3 sucrose solution in order to maintain the organelles osmotic integrity. The respiratory substrate used by mitochondria is glucose, not sucrose.
November 2004 - Q38
Used for growth + used for other life process + respiratory heat losses( But this hw yu get the answers but i m nt sure y)
June 2004 - Q32 ans D
diffuses through the squamous epithelial cells of the alveolar wall and then through the endothelial cells of
the capillary wall or they failed to understand that the oxygen crosses two cell surface membranes as it
diffuses into and then out of each cell. The fifth membrane is, the surface of the red blood cell.
June 2002 -
Q 14 ans B
The substrate concentration is high the And the is nt free for the enzymes so the substrate molecules Wait for their turn
Q18 Ans C
Thank you very much, I saw this today in the morning before heading to school :)
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After 2days i am having a class test on water and carbohydrates. Please post as many typical questions along with answers that i may get in common. wud appreciate any help(__)
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how to remember/memrise details ..
better option than muggin?
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how to remember/memrise details ..
better option than muggin?
Biology wont require 'mugging-up' if you understand the concepts clearly.
After 2days i am having a class test on water and carbohydrates. Please post as many typical questions along with answers that i may get in common. wud appreciate any help(__)
It's a class test, so ofcourse we cant 'predict' the questions. However, I have attached a document of related questions. If you find difficulty in answering any of the questions; either post your doubts here.... or google search the answers. ::) :P
Good Luck!
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How can I get the uncertainty in the measurement of the actual thickness of a leaf lamina? Please help me out... :-\
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Add the uncertainties at either end. For instance, if your ruler measures to the nearest mm, that is +-0.5mm at either end so 1mm is the uncertainty and the meaurement is +-1mm
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Guys is this right , in the codons ,
A can be U or T or C
T can be A or G
C can be C or G
G can be T or C
Another question
There was a question in p1 that says we need only 8 essential amino acids , which chapter does it state that?
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Guys is this right , in the codons ,
A can be U or T or C
T can be A or G
C can be C or G
G can be T or C
I didn't quite understand what you mean by this question. But, during pairing of the DNA...
A binds with T and
C binds with G
in RNA the 'T' is replaced by 'U'.
Another question
There was a question in p1 that says we need only 8 essential amino acids , which chapter does it state that?
I guess, that statement was based on the question itself. There are 20 amino acids we know about, not 8.
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can anyone pls give a description how starch/tile test is carried out??=S.i know about starch test using iodine solution and all but how is it carried out using a tile?and also,in case you get the wrong idea,it isnt about putting a leaf on tile and testing it.
my teacher told us all to get it tomorrow and i have no idea what it is.
Hope i get the answer soon.thanks!
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can anyone pls give a description how starch/tile test is carried out??=S.i know about starch test using iodine solution and all but how is it carried out using a tile?and also,in case you get the wrong idea,it isnt about putting a leaf on tile and testing it.
my teacher told us all to get it tomorrow and i have no idea what it is.
Hope i get the answer soon.thanks!
Here you are, it explains it well ;)
http://www.footprints-science.co.uk/Starch.htm
Understand it first, then put it in your own words ;)
COnfirmation : http://www.practicalbiology.org/areas/introductory/energy/photosynthesis/testing-leaves-for-starch-the-technique,73,EXP.html
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THANKYOU deadlyking!!=)these websites are really good.
Thanks again!
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THANKYOU deadlyking!!=)these websites are really good.
Thanks again!
Anytime buddy ;)
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I have trouble with the conversion questions...Like if they give a picture of a cell...When measured with a scale, its 3 cm long...How do I convert this value to micrometers...?
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Biology practicals on the 8th:'( any advice?
And can someone please explain serial dilution!?
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I have trouble with the conversion questions...Like if they give a picture of a cell...When measured with a scale, its 3 cm long...How do I convert this value to micrometers...?
Check out the conversion factors.
1 Centimeter = 10,000 Micrometers
1 Micrometer = 0.0001 Centimeters
Therefore, 3cm=30,000 micrometers.
Biology practicals on the 8th:'( any advice?
And can someone please explain serial dilution!?
Practicals are supposed to be easy papers. Practise plan diagrams and calculations
Serial Dilutions. (http://www.woodrow.org/teachers/esi/2002/Biology/Projects/lab_skills/ls8/)
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Does anyone have specific advice on plan diagrams or taking readings? Such as, significant figures? How much detail does drawings of [magnified] cells require?
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Does anyone have specific advice on plan diagrams or taking readings? Such as, significant figures? How much detail does drawings of [magnified] cells require?
I will try uploading some notes on it by day after tomorrow. Just send me a PM if I forget.
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Hi!
http://www.xtremepapers.com/CIE/International A And AS Level/9700 - Biology/9700_s03_qp_1.pdf
q, 7 , 18 and 25.
http://www.xtremepapers.com/papers/CIE/Cambridge%20International%20A%20and%20AS%20Level/Biology%20(9700)/9700_s03_qp_2.pdf
http://www.xtremepapers.com/papers/CIE/Cambridge%20International%20A%20and%20AS%20Level/Biology%20(9700)/9700_s03_ms_1+2+3+4+5+6.pdf
Ans 6 c part, marking scheme gives two answers for this question. which points to be considered.
Thank you.
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can someone plzz solve this MCQ for me and explain?
a sample of swimming pool water contains 0.482 ppm of chlorine.this is equal to a percentage of
A.0.000482
B.0.0000482
C.0.00000482
D.0.000000482
this is from edexcel chem 1
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can someone plzz solve this MCQ for me and explain?
a sample of swimming pool water contains 0.482 ppm of chlorine.this is equal to a percentage of
A.0.000482
B.0.0000482
C.0.00000482
D.0.000000482
this is from edexcel chem 1
Answer is B.
ppm - particles per million meaning 106
% - 100 meaning 102
From here it's basic equation
Ans = (0.482/106)*102 = 0.0000482
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Yes divide by 10^6 to change to proportion and times by 100 to change to percentage