Exam Question Log

Question 1

The movement of Na+ out of the cell allows the absorption of glucose into the
cell lining the ileum.
Explain how

Answer 1

Maintains a concentration gradient for Na+ from cell lining ileum
Na+ moves in by co transport bringing glucose with it

Question 2

Figure 2 shows the SGLT1 polypeptide with NH2 at one end and COOH at the
other end.
Describe how amino acids join to form a polypeptide so there is always NH2 at
one end and COOH at the other end.
You may use a diagram in your answer

Answer 2

1. One amine/NH2 group joins to a
   carboxyl/COOH group to form a peptide
   bond;
2. (So in chain) there is a free amine/NH2 group
   at one end and a free carboxyl/COOH group
   at the other

Question 3

To study lipid digestion, a scientist placed a tube into the gut of a healthy
20-year-old man. The end of the tube passed through the stomach but did not reach
as far as the ileum.
The scientist fed the man a meal containing triglycerides through the tube.
The scientist also used the tube to remove samples from the man’s gut at intervals
after the meal.
The scientist measured the type of lipid found in the samples. Some of her results are
shown in Table 1.
Table 1
Sample Time of collection
after meal / min
Concentration of
fatty acids / mg cm−3
Concentration of
triglycerides / mg cm−3
A 45 2.7 0.6
B 75 3.3 0.0
0 2 . 1 Use your knowledge of lipid digestion to explain the differences in the results for
samples A and B shown in Table 1.
You should assume that no absorption had occurre

Answer 3

Triglycerides decrease because of the action of
lipase
OR
Fatty acids increase because of the action of
lipase;
2. Triglycerides decrease because of hydrolysis (of
triglycerides)
OR
Fatty acids increase because of hydrolysis (of
triglycerides);
3. Triglycerides decrease because of digestion of
ester bonds (between fatty acid and glycerol)
3 Triglycerides
decreasing or fatty
acids increasing only
need to be stated
once.
Accept
‘lower/higher/quoted
numbers’ for
‘decrease/increase’.
OR
Fatty acids increase because of digestion of
ester bonds (between fatty acid and glycerol);

Question 4

At P on Figure 3, the pressure in the left ventricle is increasing. At this time, the rate
of blood flow has not yet started to increase in the aorta

Answer 4

1. Aortic/semi-lunar valves is closed;
2. Because pressure in aorta higher than in
   ventricle;

Question 5

At Q on Figure 3 there is a small increase in pressure and in rate of blood flow in the
aorta.
Explain how this happens and its importance

Answer 5

2 1. Elastic recoil (of the aorta wall/tissue);
2. Smooths the blood flow
OR
Maintains rate of blood flow
OR
Maintains blood pressure

1. Reject muscle
   contracting.
2. Ignore reference to
   muscle relaxing.
3. Ignore reference to
   preventing backflow
   of blood

Question 6

A different student did this investigation. He did not have a colorimeter.
Describe a method this student could use to prepare colour standards and use them
to give data for the total anthocyanin extracted.

Answer 6

.4 1. Use known concentration of blueberry
juice/extract
OR
Use known concentration of
anthocyanin/pigment (solution)
OR
Use known concentration of (extraction) solvent
to be added to blueberries;
2. Prepare dilution series;
3. Compare (results) with colour standards to give
score/value/concentration;

Question 7

Describe the role of DNA polymerase in the semi-conservative replication of DNA.
[2 marks]

Answer 7

1. Joins (adjacent DNA) nucleotides;
2. (Catalyses) condensation (reactions);
3. (Catalyses formation of) phosphodiester bonds
   (between adjacent nucleotides);
4. Reject suggestions
   that it forms
   hydrogen bonds or
   joins
   complementary
   bases.
5. Reject ‘nucleotide
   bases’.

Question 8

Cyclin D stimulates the phosphorylation of DNA polymerase, which activates the
DNA polymerase.
Describe how an enzyme can be phosphorylated

Answer 8

3 1. Attachment/association of (inorganic) phosphate
(to the enzyme);
2. (Released from) hydrolysis of ATP
OR

Ignore named
bonding or position
of phosphate
attaching to
enzyme but reject
formation of E-S
complex.

(Released from) ATP to ADP + Pi;

Question 9

Particulate matter is solid particles and liquid particles suspended in air. Polluted air
contains more particulate matter than clean air.
A high concentration of particulate matter results in the death of some
alveolar epithelium cells. If alveolar epithelium cells die inside the human body they
are replaced by non-specialised, thickened tissue.
Explain why death of alveolar epithelium cells reduces gas exchange in human lungs.
[3 marks

Answer 9

1. Reduced surface area;
2. Increased distance for diffusion;
3. Reduced rate of gas exchange

Question 10

Figure 5 shows the percentage of rat cells undergoing DNA replication. Some cells
contained a protein called cyclin D and some cells did not contain cyclin D. All cells
were in early interphase at time 0.

Some tumour cells contain higher than normal concentrations of cyclin D.
Use Figure 5 to suggest why higher than normal concentrations of cyclin D could
result in a tumour.

Answer 10

1. Shortens interphase
   OR
   Cells begin DNA replication earlier
   OR
   DNA replication (starts) faster;
2. Fast(er) cell cycle/division/multiplication/mitosis
   OR
   Uncontrolled cell division/mitosis;
3. (Resulting in) a mass/group of
   abnormal/excessive cells
4. Accept ‘starts
   mitosis earlier’.
5. Accept ‘(May result
   in) mutation in a
   tumour suppressor
   gene’ OR ‘(May
   result in) mutation
   in an oncogene’.
   2 and 3. Ignore
   uncontrolled
   growth;
6. Accept ‘(Resulting
   in) a growth of
   abnormal/excessive
   cells’.

Question 11

Scientists investigated the genetic diversity between several species of sweet potato.
They studied non-coding multiple repeats of base sequences.
Define ‘non-coding base sequences’ and describe where the non-coding multiple
repeats are positioned in the genome

Answer 11

1. DNA that does not code for protein/polypeptides
   OR
   DNA that does not code for (sequences of)
   amino acids
   OR
   DNA that does not code for tRNA/rRNA;
2. (Positioned) between genes;
3. Do not credit ‘DNA
   that does not code
   for an amino acid’.
4. Ignore reference to
   introns.
5. Reject (positioned)
   ‘in introns’ or
   ‘between exons’.
6. Accept
   ‘(Positioned) at the
   end of
   chromosomes’ or
   ‘(Positioned) in the
   telomeres’.

Question 12

The scientists studied five individuals from each species. Within the five individuals of
species T they found a percentage similarity of 66%.
Use Table 3 to evaluate how this information affects the validity of the
phylogenetic tree

Answer 12

1. (Supported) more similar than with any other
   species;
2. (Not supported) high (intraspecific) variation in
   species T (compared with variation between T
   and C);
3. Small sample

Question 13

A journalist saw Figure 10 and suggested that future increases in atmospheric
carbon dioxide concentration could result in less transpiration.
Evaluate his suggestion.

Answer 13

1. Increasing carbon dioxide (concentration) shows
   decreased stomatal density;
2. Fewer stomata means less transpiration
   OR
   Fewer stomata means less evaporation (of water
   from leaves)
   OR
   Fewer stomata means less diffusion of water
   vapour (from leaves);
3. Same (volume of) carbon dioxide can be
   absorbed for photosynthesis with smaller number
   of stomata;
4. Don’t know the size of the stomata;
5. Don’t know whether leaf size has changed;
6. Don’t know if this is true for all species (of plant);
7. Don’t know how long the stomata are open for;
8. Don’t know if this trend will continue (beyond the
   concentrations of carbon dioxide shown in Figure
   10);
9. Other factors affect transpiration (rate);

Question 14

Describe how mRNA is formed by transcription in eukaryotes.

Answer 14

1. Hydrogen bonds (between DNA bases) break;
2. (Only) one DNA strand acts as a template;
3. (Free) RNA nucleotides align by complementary
   base pairing;
4. (In RNA) Uracil base pairs with adenine (on
   DNA)
   OR
   (In RNA) Uracil is used in place of thymine;
5. RNA polymerase joins (adjacent RNA)
   nucleotides;
6. (By) phosphodiester bonds (between adjacent
   nucleotides);
7. Pre-mRNA is spliced (to form mRNA)
   OR
   5 max Introns are removed (to form mRNA);

Question 15

Describe how a polypeptide is formed by translation of mRNA.

Question 16

Describe how a polypeptide is formed by translation of mRNA

Answer 16

1. (mRNA attaches) to ribosomes
   OR
   (mRNA attaches) to rough endoplasmic
   reticulum;
2. (tRNA) anticodons (bind to) complementary
   (mRNA) codons;
3. tRNA brings a specific amino acid;
4. Amino acids join by peptide bonds;
5. (Amino acids join together) with the use of ATP;
6. tRNA released (after amino acid joined to
   polypeptide);
7. The ribosome moves along the mRNA to form
   the polypeptide

Question 17

Define ‘gene mutation’ and explain how a gene mutation can have:
• no effect on an individual
• a positive effect on an individual

Answer 17

X

Question 18

Explain the change in ATP concentration with increasing inorganic phosphate concentration [ 2marks]/

Answer 18

There will be more enzyme-substrate complexes forming causing an increase in atp concentration.

At/above 40 all active sites are occupied

Question 19

Explain the advantage for larger animals of having a spec