unit 1 2011 January

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 / nuclear envelope / nuclear membrane /
nucleolus;
-Mitochondrion;
-(Smooth / rough) ER;
-Lysosome;
-Microvillus / brush border;
-Golgi;
-Linear / non-circular -DNA / chromosome;
-80S / denser / heavier / larger ribosomes;

Question 2

Give one advantage of using a TEM rather than a SEM

Answer 2

Higher resolution / higher (maximum) magnification /
higher detail (of image);
OR
Allows internal details / structures within (cells) to be
seen / cross section to be taken;

Question 3

Give one advantage of using a SEM rather than a TEM.

Answer 3

Thin sections do not need to be prepared / shows

surface of specimen / 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 fixed (shape) / is
rigid / does not wrap around substrate / (already) fits the
substrate / is complementary (before binding);

Question 6

Use the diagram and your knowledge of enzymes to explain how sulfanilamide
prevents bacteria producing folic acid.

Answer 6

Similar structure / shape (to PABA) / both
complementary;
Competes for / binds to active site / competitive inhibitor;
Less PABA binds / less E-S complexes;
OR
Specific reference to different structure / shape (to
PABA) using the diagram;
Binds to position other than active site / binds to allosteric
site / binds to inhibitor site / non-competitive inhibitor;
Changes the active site so substrate cannot bind / less
PABA binds / less E-S complexes;

Question 7

Which of the blood vessels carries oxygenated blood to the heart

Answer 7

Pulmonary Vein

Question 8

Which of the blood vessels carries deoxygenated blood to the lungs?

Answer 8

Pulmonary artery

Question 9

Explain, in terms of pressure, why the semilunar valves open.

Answer 9

Pressure is greater below valve / in ventricle than

(artery);

Question 10

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 10

1) Allow atria to empty / contract / ventricles to fill;
Before ventricles contract;

2) Delays contraction of ventricles;
Until after atria have contracted / ventricles have filled;

Question 11

Omega-3 fatty acids are unsaturated. What is an unsaturated fatty acid?

Answer 11

Double bond(s);
(Bonds) between carbon;

Question 12

A triglyceride does not contain sucrose or glycosidic bond

Give one other way in which the structure of a triglyceride is different to olestra.

Answer 12

Contains glycerol / three fatty acids / forms three ester

bonds;

Question 13

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

Answer 13

1)Water will affect the mass / only want to measure water
taken up or lost;

2) Amount of water on cylinders varies / ensures same
amount of water on outside;

Question 14

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

Answer 14

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

Question 15

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

Answer 15

Girls are not sexually active / not likely to carry HPV /
vaccine may not work if already infected / few girls
sexually active (at this age)

Question 16

Explain why this vaccine

may not protect against other types of this virus.

Answer 16

Other (HPV) types have different antigens;
No memory cells for other types / memory cells not
activated;
Antibodies cannot attach to antigen / correct antibodies
not produced / antibodies are not complementary;

Question 17

Three injections of the vaccine are given Use your knowledge of
immunity to suggest why

Answer 17

More antigen;
More memory cells;
So more antibodies produced / antibodies produced
quicker (if infected);

Question 18

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

Answer 18

1) Cancer takes years to develop / develops later in life;
2) Takes time for females to become sexually active /
females must become sexually active to obtain data;
3) Few people / only teenagers vaccinated

Question 19

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

Answer 19

(Cervical cancer) can be caused by other types of HPV /
other factors / example given;
OR
(Some) women may have been infected (with HPV)
before receiving the vaccine;
OR
(As a precaution) in case vaccine does not work / a way
of monitoring if the vaccine has worked ;

Question 20

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

Answer 20

Virus cannot replicate / is destroyed / is not carried (in
vaccinated people);
Non-vaccinated people more likely to contact vaccinated
people;

Question 21

Describe the transmission and course of infection of pulmonary tuberculosis.

Answer 21

1) (Bacteria transmitted in) droplets / aerosol;
2) (Bacteria) engulfed / ingested by phagocytes /
macrophages;
3) (Bacteria) encased in named structure e.g. wall /
tubercle / granuloma / nodule;
4) (Bacteria) are dormant / not active / not
replicating;
5) If immunosuppressed, bacteria activate / replicate
/ released;
6) Bacteria destroy alveoli / capillary / epithelial
cells;
7) (Leads to) fibrosis / scar tissue / cavities
/calcification;
8) (Damage) leads to less diffusion /less surface
area / increases diffusion distance;
9) (Activation / damage allows bacteria) to enter
blood / spreads (to other organs);

Question 22

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

Answer 22

1 Alveoli break down / collapse / rupture / walls
thicken;
2 Less surface area / increases diffusion distance /
less diffusion;
3 Loss of elastin / elastic tissue / elastase involved;
4 (Alveoli / lungs) cannot recoil / spring back / have
reduced elasticity / more difficult to expel air;
5 Reduced diffusion gradient / air not replenished /
less air leaves lungs;
6 Less oxygen enters blood / tissues;
7 Less respiration / less energy released / less ATP
produced;