Prokaryotes lack a nucleus.
protocists are eukaryotic, so it consists of a nucleus.
Greetings !
I have a question ,
In my book the drawing of a normal animal cell is different to a 'liver cell' , i can see that liver cell has the following extra:
Ribosomes on endoplasmic reticulum
a 10x bigger mitochondria!!
should i mark the difference? so when i come to draw a liver cell should you add those 2?
thx in advance !
• Describe the importance of diffusion of gases
and solutes and of water as a solvent
THX
Importance of diffusion of gases :+ rep thx!
Carbon dioxide and Oxygen diffuse in and out of leaves. They are required for both respiration and photosynthesis (the two most important processes for life to occur).
Diffusion of solutes :
Transport of materials. Water or the solution acts as transport medium. Example : blood
Water as a solvent :
1. This is important as it allows ions and polar molecules to move freely within itself. Some specific ions are essential for survival of plants (e.g). They dissolve in water to get it specific cells.
2. Oxygen and carbon dioxide diffuse within a layer of moisture around mesophyll cells in order to get in. It facilitates diffusion.
Hope it helps :)
Again water acts as a transport medium.
Thanks a lot King. Do you mind if I add exactly same stuff to the bunch of bio notes?Not at all Vin. Am just glad being able to help :)
Hey guys, can someone explain to me the meaning of negative feedback? Its in the homeostasis lesson about the hypothalamus.
Is it needed in any other lesson for the 2010 exams?
Much appreciated.
Acash09
This is a small part of the syllabus and I've hardly come across any questions when I was doing my igz but you need to know what negative feedback is.
Homeostasis is the maintenance of constant internal conditions. It is often controlled be negative feedback There are six different things which need to be kept constant
Removal of carbon dioxide
Removal of urea
(Of these two we don’t need any of them, they are constantly being produced by the body and we need to constantly get rid of them.)
Ion content
Water Content
Sugar content
Temperature
Amount of thyroxin
(We need these four in certain amounts, and too much can be dangerous.)
The hypothalamus (or thermoregulatory gland) is located just above the pituitary gland. It contains sensors which monitor blood temperature and water content, and send nerve impulses to the pituitary gland. It also monitors carbon dioxide which is removed by the lungs in exhaled air. The kidneys control water content (via ADH) and ion content of the blood. The pituitary gland produces ADH for the kidneys, while the skin helps control the body temperature by sweating and raising hairs. The muscles can shiver to increase temperature. Finally the liver and pancreas work together to keep the blood sugar levels correct.
The pituitary gland secrets thyroid stimulating hormone, and the more secreted the more thyroxin is made. However, if too much thyroxin is made then it goes back to the pituitary gland and tells it to stop making so much thyroid stimulating hormone.<< when there is excess of a certain hormone, the hormone acts as an inhibitor in itself and stops its own production..This is negative feedback.
You need to be able to describe the function of the kidney in removing urea/excess water for Core, and need to be able to outline the structure of the kidney and structure + functioning of the nephron for Supplement, including the role of the renal capsule and the tubule.
Only negative feedback loops for maintenance of temperature in skin (Core) and maintenance of glucose content via insulin/glucagon (Supplement) are needed for IGCSE. At least that's what it says on the 2010 Syllabus.
Thanks very much Garfield! (I like garfield too! lol!)
Another question -
State the advantages and disadvantages of asexual reproduction
&
State the advantages and disadvantages of sexual reproduction
acash09
Thanks guys and gals! Need something else, lol!
The drugs section in the syllabus - if someone has notes, could you post it here please?
I hate the drugs section ( except the good ones - antibiotics ), i never got those notes from my friends.
Much appreciated.
Acash09 - I'll keep smilin'! :P ;D
Thanks guys and gals! Need something else, lol!
The drugs section in the syllabus - if someone has notes, could you post it here please?
I hate the drugs section ( except the good ones - antibiotics ), i never got those notes from my friends.
Much appreciated.
Acash09 - I'll keep smilin'! :P ;D
I think we need to rename this thread into "Acash09 - asking many boilogy doubts!" lol! ::)
Sorry, i've taken a lot of your time people, but i appreciate your help!
Another doubt - in 7.1.2 transpiration -
"discuss the adaptations of the leaf, stem and root to three contrasting environments, to include pond, garden and desert, with emphasis on local examples (where appropriate) and the factors described in the core"
&
7.1.3 translocation
"compare the role of transpiration and translocation in the transport of materials from sources to sinks, within plants at different seasons"
I know this is becoming to much but my igcse are getting nearer and nearer and i dont have time to look here and there for answers so please bear with me a few questions more :P
thanks again! acash09
Another doubt - in 7.1.2 transpiration -
"discuss the adaptations of the leaf, stem and root to three contrasting environments, to include pond, garden and desert, with emphasis on local examples (where appropriate) and the factors described in the core"
Xerophytes (Desert plants)
They are plants that are able to exist in conditions where water is scarce. Cacti are xerophytes that survive in hot, dry (arid) desert regions. Cacti reduce water loss and conserve water in the following ways:
1) Their leaves are reduced to spines. This reduces the surface area of the leaf over which water can be lost.
2) A thick waxy cuticle covers the plant's surfaces and reduces transpiration.
3) They have swollen stems containing water-storage tissue.
4) They have a shallow, spreading root system to absorb quickly any water from rain and overnight condensation.
5) Many cacti have a round compact shape which reduces their surface area so there is less surface through which water can be lost.
6) They have shiny surfaces which reflect heat and light.
7) Their stomata are closed during the day to reduce water loss. They open their stomata at night to absorb the carbon dioxide which they store for use in photosynthesis during the day. Photosynthesis occurs in the outer layers of cells in their stems.
Hydrophytes (Pond plants)
(eg. Water lilies, Nymphaea sp.)
They are plants that grow submerged or partially submerged in water. Living in water has both its costs and benefits.
Buoyed up by water and with no need for water transport, floating plants save energy since they produce little or no xylem tissue.
Roots, if present, are for anchorage and since there is no need for the roots to absorb water or mineral ions, there are no root hairs. The leaves and stems of hydrophytes have little or no cuticle, since there is no need to conserve water.
The problem for hydrophytes is that carbon dioxide, which is needed for photosynthesis, diffuses through the water much more slowly than it does through air. The same applies for oxygen, needed for plant respiration, since it is not very soluble in water. Therefore many hydrophytes have an extensive system of air spaces in their stems and leaves through which gases diffuse quickly. These air spaces provide buoyancy to keep the plants close to the light and are a resevoir of oxygen and carbon dioxide.
Mesophytes (Garden plants)
(eg. Coleus, Solenostemon spp. - brightly coloured garden plants)
Garden plants are grown for their colourful, scented flowers, for their subtle leaf colours, for shade and to provide an attractive environment.
Mesophytes are terrestrial plants that usually have enough water and do not have such extreme adaptations to reduce water loss like those of xerophytes, Many garden plants are mesophytes, as gardeners can provide them with enough water even in parts of the world that might be dry for much of the year.
Quick question: describe the use of microorganisms in the food industry, with reference to yoghurt and single cell protein.1.Two species of bacteria Lactobacillus bulgaricus and Lactococcus thermophilus in approximately equal proportions, are used to make yoghurt.
Thanks in advance
1.Two species of bacteria Lactobacillus bulgaricus and Lactococcus thermophilus in approximately equal proportions, are used to make yoghurt.
NOTE : You need not know the names of the bacteria. I just mentioned it ;)
Commercial producers pasteurize and homogenize the milk before adding the starter. After stirring, the mixture is then incubated for 3-6 hours at 40-450C. At this temperature the two bacteria have a mutually stimulating effect on one another.
Protolytic enzymes from L. bulgaricus break down milk proteins into peptides. These stimulate the growth of L. thermophilus which, in turn, produce formic acid and carbon dioxide, growth stimulants for L. bulgaricus. As the incubation proceeds, L. bulgaricus converts the lactose to lactic acid and the pH falls to 4.2-4.4 which leads to the coagulation of proteins by lactic acid and the thickening of the yoghurt.
Further processing involves the addition of flavour, colour, fruit pulp and heat treatment to kill off any bacteria.
2.The most common single-celled protein is yeast. It is used in the manufacture of bread and beer.
The principal dry ingredients used in bread-making are wheat flour, salt, sugar, ascorbic acid, and the yeast Saccharomyces cerevisiae. Water or milk is added to produce a thick, sticky dough which is repeatedly folded or kneaded, to create nuclei for gas production and expansion. The mixed dough is rested, folded, and moulded and in a humid atmosphere at 34-350C, it is left for 10 minutes to ‘prove’.
During the process of ‘proving’, fermentation of sugars in the dough, catalysed by enzymes from the yeast cells, produces carbon dioxide. As this gas cannot escapes from the sticky mass, it fills the gas nuclei and causes the dough to “rise” or increase in volume. This process is sometimes is called ‘leavening’. The overall effects of leavening are to make the dough lighter, more digestible, and of better flavour following from the production of organic acids, alcohols and esters by yeast cells. The role of enzymes in the process are summarized as follows:
maltase
a) Maltose ---------------› glucose
(in flour) (from yeast)
invertase
b) Sucrose-----------------› glucose + fructose
(added) (from yeast)
zymase
c) Glucose + fructose----------------› alcohol + carbon dioxide
(from yeast)
The yeast fermented bread have better flavour and texture as compared to the one prepared by using baking powder therefore in the commercial production of bread, Baker’s yeast is used. The living cells of aerobically grown Saccharomyces cerevisiae are collectively referred to as baker’s yeast.
Baker’s yeast is commercially available either as a dried powder i.e. dry yeast with about 95% dry weight or in the form of cakes (about 25-30% dry weight). In recent years, some workers have reported the development of genetically engineered strains of Saccharomyces cerevisiae with improved fermentation properties.
NOTE : Again you need not know the names of the yeast.
Hope it helps :)
Thanks heaps man!
and vin tyt :P but i think gg sorted it out for me already . thanks
woah gg thanks alot ! i have some reading 2 do !!
and vin tyt :P but i think gg sorted it out for me already . thanks
I'd already started typing stuff. :P Thanks a lot GG. :)
Describe the role of the fungus penicillium in the production of the antibiotic penicillin
cheers !
yo yoIt's not talking about the diffusion of water(osmosis) - it is about the diffusion of sugar
guys this question is weird , its answer is A
but ..if its 10% sugar , that means it has 90% water and the one in the bag has 80% , so the movement shoudl be the other way round right?
thx
cheers thx + repNo problem :D
another question.. why is it A?
cheers thx + rep
another question.. why is it A?
alright cheers thx for ur timeNot a problem :D
lol thx gg ! i understood it
DESCRIBE THE PROCESS OF ASEXUAL REPRODUCTION IN POTATO PLANTSTHANK YOU :) +REP
Potatoes are stem tubers.The parent plant photosunthesises and stores the food produced in underground stems called rhizomes,which swell to form tubers.Each tuber contains stored starch,and there are buds in depressions in the surface known as eyes.In suitable conditions the buds use the stored food to form shoots,from which roots also develop.Each tuber can form a new plant.
No problem sis :D
Advantages To Asexual Reproduction-
- There is no dispersal in vegatative propogation,hence offspring will grow in the same favourable environemnt as the parent.
-They store large amounts of food that allow rapid growth when conditions are suitable.
Disadvantages To Asexual Reproduction-
-Lack of dispersal in potato tubers can lead to competitions for nutrients,water and light,and will consequently cause the plant to be less healthy.
-There is little variation creted so adaptation to changing environment is unlikely.
-If the parent potato plant has no resistance to a particular disease,none of the offspring will have resistance.
Advantages To Sexual Reproduction-
-There is variation in the offspring so adaptation to the changing or new environment is likely,enabling survival of the species.
-New varieties can be created, which may have resistance to disease.
-In plants, seeds are produced, which allow dispersal away from the plant, reducing competition.
Disadavantages-
-Two parents are usually needed(though not always- some plants can self-pollinate)
-Growth of a new plant to maturity frm a seed is slow.
cheeeeeeeeeers ;DOops :-[ hehe Sorry :D
ps:im a guy :P
thx again ::)
is there any specific way to know how to put which one as x axis and y axis? or use common sense?
here.
I hope these help ;the igcse tips will be very useful but i wanted pure igcse answers not randomly answered question :P like i said i have it in my book already :/
http://wenku.baidu.com/view/7d19506527d3240c8447ef68.html
http://answers.yahoo.com/question/index?qid=20080123022356AAiisjm
http://www.clickbiology.com/igcse-enzymes-worksheets-cambridge/
=]
Here :THANK YOU THANK YOU THANK YOU THANK YOU THANK YOU THANK YOU THANK YOU THANK YOU THANK YOU THANK YOU THANK YOU THANK YOU THANK YOU THANK YOU THANK YOU THANK YOU THANK YOU THANK YOU THANK YOU THANK YOU THANK YOU THANK YOU THANK YOU THANK YOU THANK YOU THANK YOU THANK YOU THANK YOU THANK YOU THANK YOU THANK YOU THANK YOU THANK YOU THANK YOU THANK YOU THANK YOU THANK YOU THANK YOU THANK YOU THANK YOU THANK YOU THANK YOU THANK YOU THANK YOU THANK YOU THANK YOU THANK YOU THANK YOU THANK YOU THANK YOU THANK YOU THANK YOU THANK YOU THANK YOU THANK YOU THANK YOU THANK YOU THANK YOU THANK YOU THANK YOU THANK YOU THANK YOU THANK YOU THANK YOU THANK YOU THANK YOU THANK YOU THANK YOU THANK YOU THANK YOU THANK YOU THANK YOU SO MUCH :) By the way can i put this in my guide ( ill credit you ) thanks so much again
the one about the Yogurt/milk as well as the One about the Dough - Sorry but I just can't seem to find that sheet.
Hope it helped =]
hey
Describe the differences between sexual and asexual reproduction
thanks
thank you :)
i have another question ???
industrial fermenter and explain the need to provide
suitable conditions in the fermenter, including aseptic precautions, nutrients, optimum
temperature and pH, oxygenation and agitation, for the growth of microorganisms
i cant seem to find any info of this in my book. i have a little but not enough a (paragraph), it just goes of the subject an rabbles on a load irrelevant stuff :o
thanks for the help :)
I have attached the presentation.Thanks Amelia.
Describe the advantages and disadvantages of breast feeding compared with bottled feeding using formula milkAdvantages:
Thank you :)
Advantages:u forgot an adnvan
1- baby receives antibodies from the mother (not provided by formula milk)
2- baby gets the best mix of nutrients
3- babies are not allergic to breast milk (some are allergic to formula milk)
4- breast fed babies do not become overweight
5- helps form a strong bond between the mother and the baby
6- breast milk is free and does not need to be sterilised
7- breast milk has a suitable temperature
Disadvantages:
1- difficulty in producing milk
2- breast feeding can be embarrassing to the mother
3- HIV can be transmitted by breast feeding
Hope i helped ;D
u forgot an adnvan
BREAST MILK IS freee
6- breast milk is free and does not need to be sterilised
What is this then ?Baburao meant in terms of price.
Baburao meant in terms of price.exactly
amul gold-11.50 rs / 500 ml.
:P
Thats what he thought.
Baburao meant in terms of price.
amul gold-11.50 rs / 500 ml.
:P
Thats what he thought.
Get yourself updated. It's not that much price. Much more than that.Fidato, no chit chatting here :P discuss ur problems and help others :P
Fidato, no chit chatting here :P discuss ur problems and help others :P
LOL. We've a new Mod, here. :P
the syllabus mentions this point 2.1 which I would like to know about it :Only 2 naming systems in IGCSE you have to know
Know that here are other classification
systems e.g. cladistics (based on RNA/
DNA sequencing data)
Only 2 naming systems in IGCSE you have to knowso you're sure ,right ??
1- Binomial nomenclature
2- cladistics
I'll assume you know what binomial nomenclature is.
and about cladistics, for IGCSE you only have to know the name (cladistics) and that it is based on DNA and RNA sequencing.
Yes, that's what I've studied.can't also fossil fuels be a classifying tool
plus the point from the syllabus says that you only have to know that there are other naming systems.
here are 2 questions as an example:
i-Name any system of classification other than binomial nomenclature. (cladistics)
ii- what does the system you've mentioned in (i) use for classifying species. (dna and rna)
I'm not sure from that.no but wikipedia I think
any articles about it?
Cladistics is hard, but you don't need to know much about it. :)look at this website I am not sure about the fossils matter,though .
Don't worry, these 2 are enough :D
can't also fossil fuels be a classifying tool
I am not sure about the fossils matter,though .
read it.foosils i'm really sorry
and do you mean:
or
fossils or fossil fuels?
HiIst. Twice - on the way there and on the way to the body.
I came across a question in a past biology theory paper today;
'State how many times a red blood cell must pass through the heart when it travels from the lungs and returns to the lungs'
and also:
'At high altitudes there is less oxygen in the air than at sea level.
Suggest how this might affect the uptake of oxygen in the alveoli'
Thanks :DDD