IGCSE/GCSE/O & A Level/IB/University Student Forum
Qualification => Subject Doubts => GCE AS & A2 Level => Sciences => Topic started by: [Spy] on May 20, 2010, 03:03:09 pm
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Hey Guys
So last paper in Bio AS, paper 2 was dam easy and so was paper 3, so i think the paper is going to be a killer :/
plus look at physics paper 1 was relatively very hard, so yeah god be with us, but since physics was full of repeated questions then so should bio so focus on past papers :)
any questions lets post them here :) and anyone predicting anything share it with us
good luck all :D
ill start with the questions myself, in one of the papers it asked
What level of organization is Responsible For the globular shape of enzymes?
- Primary
- Secondary
- Tertiary
- Quaternary
it should be quaternary but its tertiary how :S
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its tertiary...
primary refers to sequence to amino acids.
secondary refers twisting of chains into alpha helix n b-pleated
tertiary refrs to bending of chains to form GLOBULAR or fibrous proteins... n lastly
quaterny refers to prosthetic group(like sulphur proteins or iron in haemoglobin)
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Correction: quaternary does not necessarily have to have a prosthetic group. quaternary structure is the arrangement of multiple folded protein or coiling protein molecules in a multi-subunit complex, i.e: more than one polypeptide chains. eg: myoglobin has one folded chain hence it has a tertiary structure. haemoglobin has 4 chains, hence a quaternary str.
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Quaternary always have a prosthetic group. like myoglobin n haemoglobin have iron as prosthetic group.
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no in my book it specifically says quaternary is for globular. :S
well it doesnt specicially say that but globular proteins part is under quaternary organization, but thanks :D
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yea but too be more specific tertiary is when there is only one polypeptide chain and in quartenary more than one , and yes tertiary structure is a part of the quartenary structure therefore it is possible that like haemoglobin they mention such as globular....
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13. HIV-1 protease is an enzyme produced by the HIV virus.
Two identical chains of 99 amino acids form the enzyme. In each chain, amino acids 25, 26 and
27 in the sequence form part of the active site.
Which orders of protein structure control the shape of the active site?
A primary, secondary, tertiary and quaternary
B primary, secondary and tertiary only
C primary and quaternary only
D quaternary only
why is the answer A?
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Which of the following are increasing the spread of malaria?
1 continued migration of people due to war and civil unrest
2 increasing carbon dioxide levels causing global warming
3 increasing resistance to antibiotics and other drugs
A 1 and 2 only
B 1 and 3 only
C 2 and 3 only
D 1, 2 and 3
the answer is D, but how does increasing carbon dioxide levels cause an increased spread of malaria?
is it because it produces an optimum temp for the female anopheles mosquito eggs to hatch?? :S
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it is because mosquitoes prefer warm temperature which is required by malarial parasite to complete their growth cycle.
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it is because mosquitoes prefer warm temperature which is required by malarial parasite to complete their growth cycle.
Thanks :)
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@unknown i think its only primary n quaternary... buh m not sure.
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What level of organization is Responsible For the globular shape of enzymes?
- Primary
- Secondary
- Tertiary
- Quaternary
it should be quaternary but its tertiary how :S
It's not quaternary. quaternary structure arises when there is more than one polypeptide chain. The very first globular,3-d structure is gotten by the tertiary structure. In proteins with the highest order of structure being tertiary are also globular, e.g Myoglobin.
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13. HIV-1 protease is an enzyme produced by the HIV virus.
Two identical chains of 99 amino acids form the enzyme. In each chain, amino acids 25, 26 and
27 in the sequence form part of the active site.
Which orders of protein structure control the shape of the active site?
A primary, secondary, tertiary and quaternary
B primary, secondary and tertiary only
C primary and quaternary only
D quaternary only
why is the answer A?
The sequence of amino acids is the primary structure. When the primary structure is in itself altered, the following structures will also suffer a setback. If the sequence of amino acids in the primary structure is hydrophilic instead of phobic, then the secondary and tertiary structure will also be different, the folding of the chain will be different, the final shape will be different. Hence if a change happens in the primary structure, the following structures will also change
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The sequence of amino acids is the primary structure. When the primary structure is in itself altered, the following structures will also suffer a setback. If the sequence of amino acids in the primary structure is hydrophilic instead of phobic, then the secondary and tertiary structure will also be different, the folding of the chain will be different, the final shape will be different. Hence if a change happens in the primary structure, the following structures will also change
Thanks :)
i didnt get the question cuz it looked retarded, Thanks again :D
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not a problem
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Q. In an animal cell which process is dependent upon cell surface area and which process is dependent upon cell volume ?
mcq number 24 , june 2007 .. help me out
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Q. In an animal cell which process is dependent upon cell surface area and which process is dependent upon cell volume ?
mcq number 24 , june 2007 .. help me out
answer is C
hormones are the only ones dependant because if the surface area is larger then more receptors will be able to identify the hormone
all the others have nothing to do with surface area, carbon dioxide is dependant of cell volume because if its larger then more cell organelles are present so more respiration occurs!
hope this helped.. :)
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Q 21, jun 07
why is it 20 ??? ??? ???
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Q 21, jun 07
why is it 20 ??? ??? ???
hey, its like
a double stranded DNAs got 120 nucleotides ..
its askin fr the max length of the poly peptide chain
so first the mRNA only uses the 60 nucleotides as the template
cus it wont use both strands ..
and then 60/3 = 20 ..
i hope i made sens ..
im horribl at explainin things ..
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hey, its like
a double stranded DNAs got 120 nucleotides ..
its askin fr the max length of the poly peptide chain
so first the mRNA only uses the 60 nucleotides as the template
cus it wont use both strands ..
and then 60/3 = 20 ..
i hope i made sens ..
im horribl at explainin things ..
i know the first part about 60 nucleotides, but why do u divide it by 3?
and Thanks anyways ;)
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1 amino acid=3 nucleotides
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1 amino acid=3 nucleotides
yea i got it, Thanks ;)
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m/j 2006 q 17
and o/n 2006 1
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m/j 2006 q 17
and o/n 2006 1
m/j Q17: if it was first put in 0.35 mol.dm-3, and no change occured then that means conc. gradient inside the cell and outside are the same, when u decrease conc. to 0.1, sucrose inside the cell will diffuse outside down a conc. gradient.
so that means that solutes r lost from the cell, increasing pressure potential.
hope this helped :)
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wont pressure potential increase if water moves into cell.
here water is moving out.
the pressure potential should decrease.
the cell will become flaccid??
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wont pressure potential increase if water moves into cell.
here water is moving out.
the pressure potential should decrease.
the cell will become flaccid??
water will not move out!! because we are not increasing the conc. of sucrose, we are decreasing it.
so that means that the sucrose will diffuse out of the cell down a conc. gradient, from an area of higher conc. ( in the cell ) to an area of lower conc. ( in the solution ).
check the possibilites in the question:
A The pressure potential of the cells will become more positive.
B The solute potential of the cell will become more negative. ( more -ve means that more solutes are being taken up into the cell, which is not happening)
C The water potential of the cells will become more negative. ( if it becomes more negative in the cell it means that sucrose is being taken in from the solution, which is not happening)
D The water potential of the solution will become less negative. ( this means that water is mpvong out of the cell and thats not happening)
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i get it now thnkx a lot :) :)
any idea on o/n 2006 q1???
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i get it now thnkx a lot :) :)
any idea on o/n 2006 q1???
anytime ;)
nov 06 :
it tells you to measure the size of a chloroplast ( measure the big one between 60 -70, its about 8 )
now from the first part of the question it shows u that:
1 unit on the stage micrometer = 80 units on the ocular eyepeice
so that means that
if... 1 = 80
then. x = 8
cross multiply ( 8/80 = 0.1)
and since the stage micrometer has small divisions of 0.1 mm, multiply the answer to the top part ( 0.1 ) by 100 to get ur answer in micrometres ( which will become 0.1 x 100 = 10 micrometres)
so the answer is B
hope this helped... :)
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hey guys one more tough question
Which function can be carried out by a mature red blood cell?
A active transport
B cell division
C phagocytosis
D protein synthesis
Now answer is A.........how is it possible......???
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hey guys one more tough question
Which function can be carried out by a mature red blood cell?
A active transport
B cell division
C phagocytosis
D protein synthesis
Now answer is A.........how is it possible......???
answer is A because if u look at the other options :
B cell division ( can not occur because there is no nucleas in the RBC, this is to increase volume available for oxygen transport )
C phagocytosis ( does not have any lysosomes, so it cannot be this option )
D protein synthesis ( as there is no nucleas, thus no DNA is present, so mRNA cannot be formed and so proteins can not be made even if there were any ribosomes )
hope you understood :)
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answer is A because if u look at the other options :
B cell division ( can not occur because there is no nucleas in the RBC, this is to increase volume available for oxygen transport )
C phagocytosis ( does not have any lysosomes, so it cannot be this option )
D protein synthesis ( as there is no nucleas, thus no DNA is present, so mRNA cannot be formed and so proteins can not be made even if there were any ribosomes )
hope you understood :)
haha thanks man did the same thing ;) this much i had gotten easily bt now try and prove A wrong even u can do that
no mitochondria........so active transport not possible....
hmmm......i tried other conclusions.......nodin seems to fit..
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haha thanks man did the same thing ;) this much i had gotten easily bt now try and prove A wrong even u can do that
no mitochondria........so active transport not possible....
hmmm......i tried other conclusions.......nodin seems to fit..
this is the stupidest question ever, veryyyyy confusing, but i think they were testing people to see if they knew that RBCs did not have a nucleas! :)
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EXACTLY............but i am sure they cannot quote wrong info is it by chance possible that mature rbc takes O2 from low conc to high...........this is just a hypothesis who noes ???
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anytime ;)
nov 06 :
it tells you to measure the size of a chloroplast ( measure the big one between 60 -70, its about 8 )
now from the first part of the question it shows u that:
1 unit on the stage micrometer = 80 units on the ocular eyepeice
so that means that
if... 1 = 80
then. x = 8
cross multiply ( 8/80 = 0.1)
and since the stage micrometer has small divisions of 0.1 mm, multiply the answer to the top part ( 0.1 ) by 100 to get ur answer in micrometres ( which will become 0.1 x 100 = 10 micrometres)
so the answer is B
hope this helped... :)
;D ;D ;D
thnkxxxxxxxxxxxx
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EXACTLY............but i am sure they cannot quote wrong info is it by chance possible that mature rbc takes O2 from low conc to high...........this is just a hypothesis who noes ???
maybe they thought it couldve been possible before, but now its proven wrong, but again who knows except god ???
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;D ;D ;D
thnkxxxxxxxxxxxx
your welcome :)