A level Biology: Post your doubts here!

[Gehad Mohamed]

what year?

 

[Ayyan :D]

Y

Yeah ,its A .Thanks agn.

No Problem.

 

[periyasamy]

Hello!
Plzz help me in Q 4/6 /
14 why D is wrong ?

18 why a?

question 18-----answer is a because dna replication occur in interphase(s-phase)
question 14----------answer d is wrong because i think enzyme has nothing to do with yield.It only affects rate.
question 6------use the formula .....measured length in ruler of given length/the value given=magnification
question 4----all can(one thing u might get confused is mitochondria-----(mitochondria-------either 70/80 s ribosome.

 

[periyasamy]

R-groups are hydrocarbons so why not CH3 ??!

I dont really get your question.But why ch3 is correct is ecause as u know r group in protein is also known as an alkyl group and ch3 is a methyl,it is an alkyl group.

 

[Gehad Mohamed]

question 18-----answer is a because dna replication occur in interphase(s-phase)
question 14----------answer d is wrong because i think enzyme has nothing to do with yield.It only affects rate.
question 6------use the formula .....measured length in ruler of given length/the value given=magnification
question 4----all can(one thing u might get confused is mitochondria-----(mitochondria-------either 70/80 s ribosome.

Thanks alot

 

[periyasamy]

Thanks alot

welcum

 

[Khadija_1234]

http://papers.xtremepapers.com/CIE/...and AS Level/Biology (9700)/9700_w06_qp_1.pdf
Please help with Q1

http://papers.xtremepapers.com/CIE/...and AS Level/Biology (9700)/9700_s07_qp_1.pdf
Need help for Q4

 

[Khadija_1234]

http://papers.xtremepapers.com/CIE/...and AS Level/Biology (9700)/9700_w07_qp_1.pdf
Q15

 

[6Astarstudent]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_w07_qp_1.pdf
Q15

from the graph we can tell that the ratio of initial to final length is increasing, meaning that the length of potato chip is decreasing.
If the chip is decreasing, it means water is taken out of the chip via osmosis.
water potential of distilled water is 0, as water is taken out the solute concentration is higher in chip (lower water potential so its more negative)
as water is taken out, it gets less turgid. (turgid occurs when too much water)

 

[6Astarstudent]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_w06_qp_1.pdf
Please help with Q1

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_s07_qp_1.pdf
Need help for Q4

Q1
from the first diagram we know that 0.2mm equates to 80 small divisions so
0.2mm/80 = 2.5 micrometers
each chloroplast is roughly 4 divisions so 2.5x4 = 10 micrometers

Q4
frist diagram we know that 0.2mm is 100 divisions so
0.2mm/100 = 2 micrometers
growth is around 10 divisions so 10x 2 = 20 micrometers in 4 hrs
divide it by time (4hr) to find rate so 20/4 = 5 micrometer / hr

 

[Khadija_1234]

from the graph we can tell that the ratio of initial to final length is increasing, meaning that the length of potato chip is decreasing.
If the chip is decreasing, it means water is taken out of the chip via osmosis.
water potential of distilled water is 0, as water is taken out the solute concentration is higher in chip (lower water potential so its more negative)
as water is taken out, it gets less turgid. (turgid occurs when too much water)

Thank you so much

 

[6Astarstudent]

An actively growing cell is supplied with radioactive amino acids.
Which cell component would first show an increase in radioactivity?
A Golgi body
B mitochondrion
C nucleus
D rough endoplasmic reticulum

D, RER because the ribosomes on the RER is the site of protein synthesis.
(protein is the folding of polypeptide chains made of amino acids)

second closest answer would be A, but Golgi is the site of protein packaging

 

[sam1234]

http://olevel.sourceforge.net/papers/9700/9700_s13_qp_12.pdf
Q19 ans is A. Explain somebody? Please.

 

[sam1234]

D, RER because the ribosomes on the RER is the site of protein synthesis.
(protein is the folding of polypeptide chains made of amino acids)

second closest answer would be A, but Golgi is the site of protein packaging

Did u get six a stars in your alevels

 

[6Astarstudent]

http://olevel.sourceforge.net/papers/9700/9700_s13_qp_12.pdf
Q19 ans is A. Explain somebody? Please.

I actually have no idea what telomere is so this is just some guesses and logical reasoning that I would have if I was to get this question in an exam,
1. telo-mere, the prefix is the same as telophase which means termination and ending
2. three quarters of the mitotic cycle is interphase so the time for replication is very short

without telomere which supposedly terminates things, division should theoretically continue endlessly
so answer should be A, if telomere is replaced with X then the division will not terminate and continue endlessly.


better do some research about it though, although I don't recall it being in the syllabus.

 

[sam1234]

I actually have no idea what telomere is so this is just some guesses and logical reasoning that I would have if I was to get this question in an exam,
1. telo-mere, the prefix is the same as telophase which means termination and ending
2. three quarters of the mitotic cycle is interphase so the time for replication is very short

without telomere which supposedly terminates things, division should theoretically continue endlessly
so answer should be A, if telomere is replaced with X then the division will not terminate and continue endlessly.


better do some research about it though, although I don't recall it being in the syllabus.[
I don't think it's linked to telophase. It's linked to mitosis cycle eventually. Anyone has an idea about this question?

 

[Lujain M.]

Can someone ease explain q 4 nov8?
And question 16 in nov10 v1.

 

[yousef]

The sequence of bases on part of a molecule of DNA is shown.

TACAAATGACCA sense strand
ATGTTTACTGGT antisense strand

What is the sequence of bases in mRNA transcribed from this sequence?
A ATGTTTACTGGT
B AUGUUUACUGGU
C TACAAATGACCA
D UACAAAUGACCA

Answer is B , why it's not D .. both are correct

 

[6Astarstudent]

Can someone ease explain q 4 nov8?
And question 16 in nov10 v1.

w08 q4
you measure the closest distance from the inner alveolar wall to the membrane of the red blood cell, which is roughly 6-8mm depending on where you measure
magnification is x2500 so 6mm or 8mm divide by 2500 = 2.4 or 3.2 micrometers
so answer is B

w10 qp11 q16
its obvious that answer is A with some physics knowledge but with the facts the question has provided
firstly it says sucrose solution with highest water potential ie. closer to 0 as water potential is generally <0.
so water will move into cell via osmosis
this means you can immediately eliminate B where the centre cells are flaccid

over all potential of plant cells in As level biology is determined by the water potential and pressure potential
the thin cell wall cells have less pressure potential so they are likely to take in more water and expand hence the only correct answer is A where the strip is flipped inside out.

 

[Lujain M.]

w08 q4
you measure the closest distance from the inner alveolar wall to the membrane of the red blood cell, which is roughly 6-8mm depending on where you measure
magnification is x2500 so 6mm or 8mm divide by 2500 = 2.4 or 3.2 micrometers
so answer is B

w10 qp11 q16
its obvious that answer is A with some physics knowledge but with the facts the question has provided
firstly it says sucrose solution with highest water potential ie. closer to 0 as water potential is generally <0.
so water will move into cell via osmosis
this means you can immediately eliminate B where the centre cells are flaccid

over all potential of plant cells in As level biology is determined by the water potential and pressure potential
the thin cell wall cells have less pressure potential so they are likely to take in more water and expand hence the only correct answer is A where the strip is flipped inside out.

Thank you a lot! Do you mind helping me with q34 nov.12 v.2?