A- level Biology paper 2 Dec mock 2020
questions with complete solutions.
Describe the role of enzymes in the digestion of proteins in a mammal. - ANSWER: 1.
(Reference to) hydrolysis of peptide bonds;
2. Endopeptidase act in the middle of
protein/polypeptide
OR
Endopeptidase produces short(er) polypeptides/
increase number of ends;
3. Exopeptidases act at end of protein/polypeptide
OR
Exopeptidase produces dipeptides/amino acids;
4. Dipeptidase acts on dipeptide/between two
amino acids
OR
Dipeptidase produces (single) amino acids;
Protein digestion begins when you first start chewing. [There are two enzymes in your
saliva called amylase and lipase. They mostly break down carbohydrates (starch) and
fats.
-Protein digestion begins with endopeptidases. The action of endopeptidases increases
the number of 'ends' that can be hydrolysed by exopeptidases. This speeds the rate of
protein digestion
- Once a protein source reaches your stomach, hydrochloric acid and protease
enzymes break it down into smaller chains of amino acids.[ which are then small
enough to be absorbed into the ileum by co transport.]]
Describe and explain the effect of increasing carbon dioxide concentration on the
dissociation of oxyhaemoglobin. - ANSWER: 1. Increases/more oxygen
dissociation/unloading
OR
, Deceases haemoglobin's affinity for O2;
2. (By) decreasing (blood) pH/increasing acidity;
Use information in "Figure 3" to explain how the seal's myoglobin dissociation curve
shows the seal is adapted for diving. - ANSWER: 1. High(er) affinity for O2 (than
haemoglobin)
OR
Dissociates oxygen less readily
OR
Associates more readily;
2. Allows (aerobic) respiration when diving/at
low(er) pO2
OR
Provides oxygen when haemoglobin unloaded
OR
Delays anaerobic respiration/lactate production;
Name the two scientists who proposed models of the chemical structure of DNA and of
DNA replication. - ANSWER: Watson and Crick
A scientist replicated DNA in a test tube. To do this, he mixed an enzyme with identical
single-stranded DNA fragments and a solution containing DNA nucleotides.
Name the enzyme used in this DNA replication. - ANSWER: DNA polymerase
Use your knowledge of semi-conservative replication of DNA to suggest:
-1. the role of the single-stranded DNA fragments
-2. the role of the DNA nucleotides.
[3 marks] - ANSWER: 1.- to act as a template strand + determines the order of bases of
new DNA strand to form identical to the original stand
2.- Forms complementary (DNA) strand;
Describe and explain the role of antibodies in *stimulating phagocytosis.*
Do not include details about the process of phagocytosis. (2 marks) - ANSWER: 1. Bind
to antigen
OR
Are markers;
2. (Antibodies) cause
clumping/agglutination
OR
Attract phagocytes;
questions with complete solutions.
Describe the role of enzymes in the digestion of proteins in a mammal. - ANSWER: 1.
(Reference to) hydrolysis of peptide bonds;
2. Endopeptidase act in the middle of
protein/polypeptide
OR
Endopeptidase produces short(er) polypeptides/
increase number of ends;
3. Exopeptidases act at end of protein/polypeptide
OR
Exopeptidase produces dipeptides/amino acids;
4. Dipeptidase acts on dipeptide/between two
amino acids
OR
Dipeptidase produces (single) amino acids;
Protein digestion begins when you first start chewing. [There are two enzymes in your
saliva called amylase and lipase. They mostly break down carbohydrates (starch) and
fats.
-Protein digestion begins with endopeptidases. The action of endopeptidases increases
the number of 'ends' that can be hydrolysed by exopeptidases. This speeds the rate of
protein digestion
- Once a protein source reaches your stomach, hydrochloric acid and protease
enzymes break it down into smaller chains of amino acids.[ which are then small
enough to be absorbed into the ileum by co transport.]]
Describe and explain the effect of increasing carbon dioxide concentration on the
dissociation of oxyhaemoglobin. - ANSWER: 1. Increases/more oxygen
dissociation/unloading
OR
, Deceases haemoglobin's affinity for O2;
2. (By) decreasing (blood) pH/increasing acidity;
Use information in "Figure 3" to explain how the seal's myoglobin dissociation curve
shows the seal is adapted for diving. - ANSWER: 1. High(er) affinity for O2 (than
haemoglobin)
OR
Dissociates oxygen less readily
OR
Associates more readily;
2. Allows (aerobic) respiration when diving/at
low(er) pO2
OR
Provides oxygen when haemoglobin unloaded
OR
Delays anaerobic respiration/lactate production;
Name the two scientists who proposed models of the chemical structure of DNA and of
DNA replication. - ANSWER: Watson and Crick
A scientist replicated DNA in a test tube. To do this, he mixed an enzyme with identical
single-stranded DNA fragments and a solution containing DNA nucleotides.
Name the enzyme used in this DNA replication. - ANSWER: DNA polymerase
Use your knowledge of semi-conservative replication of DNA to suggest:
-1. the role of the single-stranded DNA fragments
-2. the role of the DNA nucleotides.
[3 marks] - ANSWER: 1.- to act as a template strand + determines the order of bases of
new DNA strand to form identical to the original stand
2.- Forms complementary (DNA) strand;
Describe and explain the role of antibodies in *stimulating phagocytosis.*
Do not include details about the process of phagocytosis. (2 marks) - ANSWER: 1. Bind
to antigen
OR
Are markers;
2. (Antibodies) cause
clumping/agglutination
OR
Attract phagocytes;
