A level Biology: Post your doubts here!

[My Name]

Thank you very much, you clear much of my doubts. And yes i am taking the O/N session. Do you take it as well?

Welcome.
I'm glad I could help.Yep,this O/N session AS Biology.

 

[My Name]

http://papers.xtremepapers.com/CIE/...nd AS Level/Biology (9700)/9700_s11_qp_21.pdf
Question 2 d ii
Please and thank you!

 

[My Name]

http://studyguide.pk/Past Papers/CIE/International A And AS Level/9700 - Biology/9700_s10_qp_23.pdf
question 3 part a i
I know one answer is tertiary because of the disulphide bond.
But what about quarternary it is because it has more than one chain?

 

[qwertypoiu]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_s11_qp_21.pdf
Question 2 d ii
Please and thank you!

When CO2 dissolves and undergoes reaction with water to form H2CO3 (catalysed by carbonic anhydrase), H+ ions are formed as the acid dissociates. The H+ ions react with haemoglobin (Hb) to form haemoglobinic acid (HHb). This causes the shape of haemoglobin to change, thus reducing its affinity for oxygen. So haemoglobin loses oxygen at places with higher concentration of CO2 (bohr effect)
Hope that makes sense.

 

[qwertypoiu]

http://studyguide.pk/Past Papers/CIE/International A And AS Level/9700 - Biology/9700_s10_qp_23.pdf
question 3 part a i
I know one answer is tertiary because of the disulphide bond.
But what about quarternary it is because it has more than one chain?

I had a look at the diagram.

Primary structure: shows sequence of amino acids. This diagram does this. So the diagram DOES show primary structure.
Secondary structure: Alpha and beta coils being formed due to hydrogen bonds interacting every three amino acids or some fixed number.
Tertiary structure: shows the geometric shape of protein formed due to various bonds between R groups of amino acids. I think this is not shown here. You're right that there is one disulfide bond here between two amino acids within the right chain, but this doesn't indicate the SHAPE of the molecule.
Quaternary structure: shows the interaction between two or more polypeptide chains to form a protein molecule. The disulfide bonds between the two chains here indicate this. You might say this also doesn't show us the overall shape, but I think that may not be important for Quaternary structure, but rather the tertiary is involved with shapes.

 

[qwertypoiu]

Oh and you had a post about glycosidic bonds in cellulose with beta glucose and blabla, I was gonna reply but it seems you took it off.
I think it would've gotten 4 marks ☺

 

[My Name]

Oh and you had a post about glycosidic bonds in cellulose with beta glucose and blabla, I was gonna reply but it seems you took it off.
I think it would've gotten 4 marks ☺

Yes I did.I guess it was fine.

I had a look at the diagram.

Primary structure: shows sequence of amino acids. This diagram does this. So the diagram DOES show primary structure.
Secondary structure: Alpha and beta coils being formed due to hydrogen bonds interacting every three amino acids or some fixed number.
Tertiary structure: shows the geometric shape of protein formed due to various bonds between R groups of amino acids. I think this is not shown here. You're right that there is one disulfide bond here between two amino acids within the right chain, but this doesn't indicate the SHAPE of the molecule.
Quaternary structure: shows the interaction between two or more polypeptide chains to form a protein molecule. The disulfide bonds between the two chains here indicate this. You might say this also doesn't show us the overall shape, but I think that may not be important for Quaternary structure, but rather the tertiary is involved with shapes.

My answer was PRIMARY and TERTIARY.

When CO2 dissolves and undergoes reaction with water to form H2CO3 (catalysed by carbonic anhydrase), H+ ions are formed as the acid dissociates. The H+ ions react with haemoglobin (Hb) to form haemoglobinic acid (HHb). This causes the shape of haemoglobin to change, thus reducing its affinity for oxygen. So haemoglobin loses oxygen at places with higher concentration of CO2 (bohr effect)
Hope that makes sense.

Oh sorry I knew this!
Sorry for wasting your time.


Thank you!

 

[qwertypoiu]

Yes I did.I guess it was fine.

My answer was PRIMARY and TERTIARY.

Oh sorry I knew this!
Sorry for wasting your time.


Thank you!

You're welcome.

Btw the answer is primary and Quaternary. Tertiary is incorrect.

Good luck for your exams

 

[My Name]

You're welcome.

Btw the answer is primary and Quaternary. Tertiary is incorrect.

Good luck for your exams

Ty!

 

[wizzzzzzzzzzzzzzzzz]

Aslam alaykum
How was bio p22 ?

 

[My Name]

Aslam alaykum
How was bio p22 ?

Waalikumasalam
It was fine.Alhamdulillah.
How was it for you?

 

[wizzzzzzzzzzzzzzzzz]

Waalikumasalam
It was fine.Alhamdulillah.
How was it for you?

Alhamdulliah
Can we discuss answers

 

[My Name]

Alhamdulliah
Can we discuss answers

Alhamdulillah.
Id suggest don't maybe after sometime.

But the other are discussing here: https://www.xtremepapers.com/community/threads/how-was-9700_w15_p22.42426/page-2#post-940255

 

[_MoHD_E]

Alhamdulillah.
Id suggest don't maybe after sometime.

But the other are discussing here: https://www.xtremepapers.com/community/threads/how-was-9700_w15_p22.42426/page-2#post-940255

Pls yar can u tell me what were the elastin questions if u remember xD

 

[My Name]

Pls yar can u tell me what were the elastin questions if u remember xD

It had alot of parts.

 

[_MoHD_E]

The parts after the mode of action and before the mrna

 

[nehaoscar]

View attachment 57272
Someone explain this please
the grade thresholds say that the maximum mark is 260 and 130
but then the components add up to 270 and 140 ...
Why do they say it as 260 and 130 then???

 

[_MoHD_E]

View attachment 57272
Someone explain this please
the grade thresholds say that the maximum mark is 260 and 130
but then the components add up to 270 and 140 ...
Why do they say it as 260 and 130 then???

Because the practical marks are adjusted and then they make the final mark

 

[A41905]

9700/12/m/j/12

21. Which statements about tRNA structure are correct?

1. There is a binding site for the attachment of a specific amino acid, as well as a different binding site for the attachment to the ribosome, in order to allow translation to occur.
2. There is a ribose-phosphate backbone with strong covalent phosphodiester bonds and areas within the polynucleotide chain where base-pairing by hydrogen bonding occurs.
3. There is a section known as an anticodon that contains the same triplet of bases as the triplet of DNA bases that has been transcribed to produce the mRNA codon.

A. 1 only
B. 1 and 2 only
C. 2 and 3 only
D. 1, 2 and 3

The answer given is B. Can anyone explain why the third statement is incorrect?
Thank you in advance

 

[My Name]

The
21. Which statements about tRNA structure are correct?

1. There is a binding site for the attachment of a specific amino acid, as well as a different binding site for the attachment to the ribosome, in order to allow translation to occur.
2. There is a ribose-phosphate backbone with strong covalent phosphodiester bonds and areas within the polynucleotide chain where base-pairing by hydrogen bonding occurs.
3. There is a section known as an anticodon that contains the same triplet of bases as the triplet of DNA bases that has been transcribed to produce the mRNA codon.

A. 1 only
B. 1 and 2 only
C. 2 and 3 only
D. 1, 2 and 3

The answer given is B. Can anyone explain why the third statement is incorrect?
Thank you in advance

Read it carefully.
There is a section known as an anticodon that contains the same triplet of bases as the triplet of DNA bases that has been transcribed to produce the mRNA codon.
Some anticodons on the tRNA would contain URACIL instead of of THYMINE.