2010 Jun Unit 5

Question 1

Does tRNA contain h bonds

Answer 1

yes

Question 2

There is a large increase in the permeability in Na+ ions. Explain why. During action potential

Answer 2

Ion channel proteins open
Sodium in
Makes inside axon less negative/depolarisation
/reaches threshold
More channels open/positive feedback

Question 3

During an action potential, the membrane potential rises to +40 mV and then falls.

Answer 3

Potassium channels open;
Potassium out;
Sodium channels close

Question 4

After exercise, some ATP is used to re-establish the resting potential in axons. Explain
how the resting potential is re-established

Answer 4

Active transport against the concentration

of sodium from axon

Question 5

LH increases, Progesterone increases. LH decreases

Answer 5

LH increase
Progesterone increases
Progesterone inhibits LH
LH falls

Question 6

Explain how an activated oestrogen receptor affects the

target cell.

Answer 6

Transcription factor binds to promoter region
Stimulates RNA Polymerase
Increase transcription

Question 7

Oestrogen only affects target cells. Explain why oestrogen does not affect other cells
in the body

Answer 7

Other cells do not have oestrogen receptors

Question 8

Oestrogen and Endoxifen are similar shape.

Answer 8

O and E are of similar shape
E binds to the receptor
Prevents transcription

Question 9

Give two characteristic features of stem cells.

Answer 9

Keeps dividing

Can differentiate

Question 10

One of the viral enzymes makes a DNA copy of the virus RNA. Name this enzyme

Answer 10

Reverse transcriptase

Question 11

The insertion of the DNA copy in one of the host cell’s genes may cause the cell to
make a non-functional protein. Explain how.

Answer 11

Causes frame shift
Changes primary structure
Changes tertiary structure

Question 12

Some of the children in the trial developed cancer. How might the insertion of the DNA
have caused cancer?

Answer 12

Affects tumour suppressor gene;
Inactivates (tumour suppressor) gene;
Rate of cell division increased

Question 13

Succinate dehydrogenase catalyses one of the reactions in the Krebs cycle. What is
the evidence from the drawing that muscle fibre S is a slow muscle fibre?

Answer 13

There are many succinate dehydrogenase
Slow fibres) have lots of mitochondria/ (slow fibres)
respire aerobically

Question 14

Use evidence from the diagram to describe the distribution of mitochondria inside the
slow muscle fibres. Explain the importance of this distribution.

Answer 14

Near edge
Short distance for diffusion of oxygen
Oxygen used by mitochondria

Question 15

You could use an optical microscope and a slide of stained muscle tissue to find the
diameter of one of the muscle fibres. Explain how

Answer 15

Measure with graticule/eyepiece scale;

Calibrate against something of known size

Question 16

A student found the mean diameter for the slow muscle fibres in a section. Give two
precautions that she should have taken when sampling the fibres. Give a reason for
each precaution

Answer 16

At random to avoid bias

A large number to be representative/minimise the effect of anomalies

Question 17

Explain how the glucagon would affect the person’s blood glucose concentration.

Answer 17

Glycogen to glucose/glycogenolysis
By activating enzymes
Gluconeogenesis

Question 18

Explain why the labelled DNA probe could be used to find out whether the haplotypes
were the same

Answer 18

complementary DNA;
Binds to both (haplotypes);
The label would show up in both

Question 19

Two hundred years ago there were many wolves in Italy. By the 1970s there were fewer than 100 wolves left. Since 1980, wolves have increased in number and have spread to France

Answer 19

Genetic bottleneck

Little genetic variation

Question 20

Suggest an explanation for the number of haplotypes in the wolves that have spread to
France.

Answer 20

All descended from Italian wolves/founder effect;

Question 21

The wolf numbers are given per unit area. Explain why

Answer 21

Allows comparison;

Different (sized) areas covered