exam q 2

Question 1

Describe the process of glycolysis. (4)

Answer 1

1. Phosphorylation of glucose using ATP;
2. Oxidation of triose phosphate to pyruvate;
3. Net gain of ATP;
4. NAD reduced;

Question 2

Explain how a resting potential is maintained across the axon membrane in a
neurone. (3)

Answer 2

1. Higher concentration of potassium ions inside and higher concentration of sodium ions outside (the neurone)
   OR
   potassium ions diffuse out
   OR
   sodium ions diffuse in;
2. (Membrane) more permeable to potassium ions (leaving than sodium ions entering)
   OR
   (Membrane) less permeable to sodium ions (entering than potassium ions leaving);
3. Sodium ions (actively) transported out and potassium ions in;

Question 3

Explain why the speed of transmission of impulses is faster along a myelinated axon
than along a non-myelinated axon. (3)

Answer 3

1. Myelination provides (electrical) insulation;
2. (In myelinated) saltatory (conduction)
   OR
   (In myelinated) depolarisation at nodes (of Ranvier);
3. In non-myelinated depolarisation occurs along whole/length (of axon);

Question 4

A scientist investigated the effect of inhibitors on neurones. She added a respiratory inhibitor to a neurone. The resting potential of the neurone changed from –70 mV
to 0 mV. Explain why. (3)

Answer 4

1. No/less ATP produced;
2. No/less active transport
   OR
   Sodium/potassium pump inhibited;
3. Electrochemical gradient not maintained
   OR
   (Facilitated) diffusion of ions causes change to 0 mV
   OR
   (Results in) same concentration of (sodium and potassium) ions (either side of membrane)
   OR
   No net movement of (sodium and potassium) ions;

Question 5

Using your knowledge of the kidney, explain why glucose is found in the urine of a
person with untreated diabetes. (3)

Answer 5

1. High concentration of glucose in blood/filtrate;
2. Not all the glucose is (re)absorbed at the proximal convoluted tubule;
3. Carrier/co-transport proteins are working at maximum rate
   OR
   Carrier/co-transport proteins/ are saturated;

Question 6

explain how two features of the calorimeter shown in Figure 2 would enable a valid measurement of the total heat energy released.

Answer 6

1. Stirrer distributes heat (energy);
2. Insulation/space/air reduces loss/gain of heat
   OR
   Insulation/space/air reduces conduction/convection;
3. Water has high (specific) heat capacity;