2010 Unit 2 Jan

Question 1

Give one feature of starch and explain how this feature enables it to act as a storage
substance.

Answer 1

• Helical /spiral/coiled;
Compact
Insoluble
• Does not affect water
potential 
Large molecule
• Does not leave cell;

Question 2

The structure of cellulose is related to its role in plant cell walls. Explain how

Answer 2

• Long/straight/unbranched chains (of glucose)
• (Joined by) hydrogen bonds;
• Form (micro)fibrils
• Provide rigidity/strength/support;

Question 3

Explain the importance of elastic fibres in the wall of the aorta

Answer 3

• Stretches/’expands’ under high pressure
• Recoils/’springs back’ under low pressure
• Smooths blood flow / maintains blood pressure

Question 4

Explain the importance of muscle fibres in the wall of an arteriole.

Answer 4

• (Muscle) contracts;

* (Arteriole) constricts /regulates blood flow (to capillaries);

Question 5

The rate of blood flow decreases from the aorta to the capillaries. Use information
from the graph to explain why

Answer 5

• Large/increase in (total) cross sectional area

Question 6

Efficient exchange of substances in the capillaries is linked to the rate of blood flow.
Explain how

Answer 6

• (More) time for exchange of substances

Question 7

Whether mutation 1 affects the amino acid sequence

Answer 7

• Has no effect / same amino acid (sequence) / same primary structure;
• Glycine named as same amino acid;

Question 8

How mutation 2 could lead to the formation of a non-functional enzyme

Answer 8

• Change in primary structure;
• Change in hydrogen/ionic bonds;
• Alters tertiary structure/active site;
• Nlonger complementary / no
enzyme-substrate complexes form;

Question 9

During which part of the cell cycle are gene mutations most likely to occur?

Answer 9

• Interphase

Question 10

Suggest why gene mutations are most likely to happen during interphase

Answer 10

• DNA/gene replication/synthesis occurs / longest stage;

Question 11

Give one environmental factor that the student should have kept constant during this
investigation. She used a potometer to measure the rate of water uptake by the shoot

Answer 11

• Light (intensity) / temperature / air movement / humidity

Question 12

The student cut the shoot and put it into the potometer under water. Explain why

Answer 12

• Prevent air entering / continuous water column;

Question 13

The student wanted to calculate the rate of water uptake by the shoot in
cm3 per minute. What measurements did she need to make?

Answer 13

• Distance and time;

* Radius/diameter/area (of capillary tube);

Question 14

The student assumed that water uptake was equivalent to the rate of transpiration.
Give two reasons why this might not be a valid assumption.

Answer 14

• (Used to provide) turgidity/support/
• (Used in) photosynthesis / (produced in) respiration;
• Apparatus not sealed/’leaks’;

Question 15

Suggest how the reservoir allows repeat measurements to be made

Answer 15

• Returns bubble (to start)

Question 16

Suggest why she made repeat measurements.

Answer 16

• Increases reliability (of results) / anomalous result can be identified;

Question 17

What is an allele?

Answer 17

• (Different) form/type/version of a gene

Question 18

Explain how the gametes with the combinations of alleles Ef and eF have been
produced.

Answer 18

• Crossing over;
• Exchange (of alleles) between chromatids/chromosomes;

•

Question 19

Use Figure 6 to describe how haemoglobin loads and unloads oxygen in the body

Answer 19

• Loading of oxygen at high p.O2;
• In lungs (haemoglobin) is (almost) fully saturated / in lungs
haemoglobin has a high affinity for oxygen;
• Unloads/releases/dissociates oxygen at low p.O2;
• Unloading linked to higher carbon dioxide concentration
•

Question 20

Heat from respiration helps mammals to maintain a constant body temperature.
Use this information to explain the relationship between the surface area to volume
ratio of mammals and the oxygen dissociation curves of their haemoglobins

Answer 20

• Smaller mammal has greater surface area to volume ratio;
• Larger SA:Vol ratio more heat lost
• Smaller mammal/larger SA:Vol ratio has greater rate of
respiration/metabolism;
• Oxygen required for respiration
•

Question 21

Suggest two ways to reduce the transmission of MRSA in hospitals

Answer 21

• Isolation
• Sterilisation of wards/equipment
• Testing (of patients

Question 22

When antibiotics are prescribed for treating patients, higher doses than the MIC are
recommended. Suggest two reasons why.

Answer 22

• May not all be absorbed;
• May be broken down /metabolised/excreted quickly;
• To kill the microorganisms/bacteria;

Question 23

Suggest two ways in which a double-blind trial improves reliability

Answer 23

• Prevents bias;

* Prevents ‘placebo’ (in volunteers);

Question 24

Use your knowledge of resistance to explain the results obtained with Norfloxacin and
drug X.

Answer 24

• No/little resistance shown to drug X
• Mutation present
• Gene/allele for (antibiotic) resistance;
• Bacteria with (antibiotic) resistance survive
• Vertical gene transmission;
• Frequency of gene/allele (for resistance) increases;

Question 25

Explain why an isotonic salt solution is

used to dilute the blood sample.

Answer 25

• Has same water potential
• No (net) water movement / osmosis;
• Cells will not swell/burst/change size;

Question 26

Describe the processes that lead to a reduction in the

genetic diversity of populations of organisms

Answer 26

• Reduced variety/number of
different alleles/DNA / reduced gene pool
• Founder effect
• A few individuals from a population become isolated
• (Genetic) bottlenecks
• (Significant) fall in size of population
• Selective breeding
• Using organisms with particular alleles

Question 27

Comparing the base sequence of a gene provides more information than comparing
the amino acid sequence for which the gene codes. Explain why

Answer 27

• Triplet code / more bases than amino
acids 
• Introns/non-coding DNA
• Same amino acid may be coded for / DNA code is
degenerate