2011 Unit 1 June

Question 1

Lactose, galactose and monosaccharide X are all reducing sugars.
After the lactose has been broken down there is a higher concentration of reducing
sugar. Explain why.

Answer 1

• 2 sugars produced

Question 2

A high concentration of galactose slows down the breakdown of lactose by lactase.
Use your knowledge of competitive inhibition to suggest why.

Answer 2

• Galactose is a similar shape/structure to lactose

Question 3

People who are lactose intolerant are not able to produce the enzyme lactase.
Explain why these people get diarrhoea when they drink milk containing lactose.

Answer 3

• Low / decreased water potential (in gut);

* Water enters gut / lumen / leaves cells by osmosis;

Question 4

Some people have used the graph to conclude that a high percentage of fat in the diet
causes breast cancer. Evaluate this conclusion.

Answer 4

• Positive correlation;
• But correlation does not show causation
• Evidence against positive correlation

Question 5

How should the students make sure that the pH of the protease solution did not
change?

Answer 5

• Use buffer

Question 6

Use the diagram to describe the effect of pH on the activity of this protease

Answer 6

• Works best at pH 6

Question 7

The two people were breathing out during the time shown. What evidence in the table
supports this statement?

Answer 7

• Volume (of air in lungs) decreases;

Question 8

Emphysema reduces the efficiency of gas exchange in the lungs. Explain why.

Answer 8

• Alveoli break down / collapse
• Epithelium walls thicken;
• Reduced surface area / increased diffusion pathway
• (So) less diffusion;
• Elastic (tissue) / not recoiling / loss of elasticity
• Reduced flow rate
• Reduced diffusion or concentration gradient;

Question 9

Give two ways in which active transport is different from facilitated diffusion.

Answer 9

• Uses energy / ATP;
• Against concentration gradient
• Does not use channel proteins / only uses carrier proteins;

Question 10

The scientists used a control group in this trial. Explain why

Answer 10

• To see the effect of the drug

Question 11

Suggest how the control group would have been treated.

Answer 11

• Placebo

* (Otherwise) treated the same;

Question 12

Describe the effect of taking the drug on acid secretion.

Answer 12

• Decrease for 3 hours;

Question 13

The maximum pressure in the ventricle is much higher than that in the atrium.
Explain what causes this.

Answer 13

• (Ventricle has) thick wall / more muscle

* So contractions are stronger / harder

Question 14

Explain how atheroma can lead to a heart attack

Answer 14

• Coronary artery / vessel is blocked/narrows;
• Restricts oxygen supply to heart muscle
• Prevents respiration / ATP production / or (heart) muscle / tissues/cells die

Question 15

Explain what is meant by an antigen.

Answer 15

• Protein on (surface of) chlamydia;

* That initiates an immune response

Question 16

After an infection with chlamydia, cells of the immune system of the mice may attack
the heart muscle cells (lines 7-8). Explain why.

Answer 16

• Antibodies/memory cells against chlamydia (protein/antigen) are present;
• Protein on heart (muscle) similar to chlamydia protein/antigen;
• T cells / antibodies (attack heart muscle cells

Question 17

Some scientists have suggested that people should be vaccinated to prevent infection
by chlamydia. Evaluate this suggestion.

Answer 17

FOR
• Prevents / reduces heart disease/attacks
• Cheaper to vaccinate than treat heart disease
AGAINST
• Vaccination costly;
• Vaccine could cause heart disease or immune response against heart

Question 18

Describe how these phagocytic white blood

cells destroy bacteria.

Answer 18

• Phagocyte recognise antigens on bacteria as foreign;
• Engulf bacteria;
• Bacteria in vacuole
• Lysosome fuses with
• Bacteria digested / hydrolysed

Question 19

The epithelial cells that line the small intestine are adapted for the absorption of
glucose. Explain how.

Answer 19

• Microvilli;
• Large/increased surface area;
• Many mitochondria;
• Mitochondria produce ATP / release or provide energy (for active transport);
• Carrier proteins for active transport;
• Channel / carrier proteins for facilitated diffusion;
• Co-transport of sodium (ions) and glucose
• Membrane-bound enzymes digest disaccharides / produce glucose