2011 Unit 1 Jan

Question 1

Name two structures present in an epithelial cell from the small intestine that are not
present in a cholera bacterium

Answer 1

• Nucleus
• (Smooth / rough) ER;
• Lysosome;
• Microvillus
• Golgi;
• Linear DNA

Question 2

Give one advantage of using a TEM rather than a SEM

Answer 2

• Higher resolution
• Allows internal details / structures within (cells) to be
seen

Question 3

Give one advantage of using a SEM rather than a TEM

Answer 3

• Thin sections do not need to be prepared /Can have 3-D images;

Question 4

Describe the induced fit model of enzyme action.

Answer 4

• Active site / enzyme not complementary;
• Active site changes (shape) / is flexible;
• (Change in enzyme allows) substrate to fit / E-S complex
to form;

Question 5

Describe one way that the lock and key model is different from the induced fit model

Answer 5

• Active site does not change (shape)/ is complementary (before binding);

Question 6

When a wave of electrical activity reaches the AVN, there is a short delay before a
new wave leaves the AVN. Explain the importance of this short delay.

Answer 6

• Allow atria to empty / contract / ventricles to fill;
• Before ventricles contract;
OR
• Delays contraction of ventricles;

Question 7

What is an unsaturated fatty acid?

Answer 7

• Double bond(s)

* (Bonds) between carbon

Question 8

Before reweighing, the student blotted dry the outside of each cylinder. Explain why

Answer 8

• Water will affect the mass

* Amount of water on cylinders varies

Question 9

The student calculated the percentage change in mass rather than the change in mass.
Explain the advantage of this.

Answer 9

• Allows comparison / shows proportional change;
• Idea that cylinders have different starting masses /
weights;

Question 10

The student carried out several repeats at each concentration of sodium chloride
solution. Explain why the repeats were important.

Answer 10

• (Allows) anomalies to be identified

* Makes the average / mean more reliable

Question 11

HPV vaccine is offered to girls aged 12 to 13 (line 5). Suggest why it is offered to this
age group.

Answer 11

• Girls are not sexually active

Question 12

The vaccine is made from HPV types 16 and 18 (line 5). Explain why this vaccine
may not protect against other types of this virus.

Answer 12

• Other (HPV) types have different antigens
• Memory cells not activated;
• Antibodies cannot attach to antigen
• Antibodies are not complementary

Question 13

Three injections of the vaccine are given (lines 5 to 6). Use your knowledge of
immunity to suggest why

Answer 13

• More antigen
• More memory cells;
• So more antibodies produced

Question 14

It will be many years before it can be shown that this vaccination programme has
reduced cases of cervical cancer (lines 7 to 9). Suggest two reasons why

Answer 14

• Cancer takes years to develop / develops later in life;
• Few people / only teenagers vaccinated;
•

Question 15

Suggest why women who have been vaccinated still need to be offered
smear tests.

Answer 15

• (Cervical cancer) can be caused by other types of HPV
• (Some) women may have been infected (with HPV)
before receiving the vaccine;

Question 16

Suggest one reason why vaccinating a large number of people would reduce
significantly the spread of HPV through the population

Answer 16

• Virus cannot replicate
• Non-vaccinated people more likely to contact vaccinated
people

Question 17

Pulmonary tuberculosis is a disease of the lungs.

Describe the transmission and course of infection of pulmonary tuberculosis.

Answer 17

• (Bacteria transmitted in) droplets / aerosol
• (Bacteria) engulfed / ingested by phagocytes
• Bacteria) encased inn wall
• (Bacteria) are not active / not
replicating;
If immunosuppressed, bacteria activate 
• Bacteria destroy capillary
• (Leads to) fibrosis
• (Damage) leads to less diffusion

Question 18

Emphysema is another disease of the lungs. People with emphysema may feel
weak and tired. Explain why

Answer 18

• Alveoli break down/walls thicken;
• Less surface area / increases diffusion distance
• Loss of elastin / elastic tissue 
• (Alveoli / lungs) cannot recoil 
• Reduced diffusion gradient
• Less oxygen enters blood / tissues
• Less respiration / less energy released / less ATP
produced;