paper 2

Question 1

Describe the process of glycolysis (4) [2021]

Answer 1

• Phosphorylation of glucose using ATP
• Oxidation of triose phosphate to pyruvate
• Net gain of ATP
• NAD reduced

Question 2

Explain how a resting potential is maintained across the axon membrane in a neurone (3) [2021]

Answer 2

• Higher conc of K+ inside and higher conc of Na+ outside
• Membrane is impermeable to Na+
• Sodium potassium pump
• 3Na+ pumped out and 2K+ pumped in
• Requires energy from ATP

Question 3

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) [2021]

Answer 3

• Less ATP is produced
• Less active transport/ Na+K+ pump is inhibited
• Can’t maintain an electrochemical gradient

Question 4

Using your knowledge of the kidney, explain why glucose is found in the urine of a
person with untreated diabetes (3) [2021]

Answer 4

• high concentration of glucose in the blood/ filtrate
• not all glucose is reabsorbed at the proximal convoluted tubule
• carrier proteins are working at a maximum rate (are saturated)

Question 5

Loss of nutrients into Lake Malawi has resulted in a decrease in some fish
populations (lines 12–13).
Explain why (4) [2021]

Answer 5

• Algal bloom blocks light
• Reduced photosynthesis and so plants die
• Saprobionts aerobically respire
• Less oxygen for fish to respire

Question 6

The mark-release-recapture method can be used to estimate the size of a fish
population (lines 13–14).
Explain how.

Answer 6

• Capture sample, mark and release
• Ensure that marking isn’t harmful to fish and doesn’t affect its survival
• Allow for fish to randomly distribute before collecting a second sample
• (n.o in sample 1 x n.o in sample 2)/ n.o marked in sample 2

Question 7

Farming cattle for humans to eat is less efficient than farming crops because of
energy transfer.
Explain why. (2) [2022]

Answer 7

• energy is lost at trophic levels
• energy is lost via respiration

Question 8

During the 48 hours, the coloured liquid moved to the left. Explain why (3) [2022]

Answer 8

• O2 is taken up by the respiring seeds
• seeds produce CO2 in aerobic respiration
• Decrease in volume

Question 9

The student used the same apparatus to determine the volume of carbon dioxide the
seeds produced during 48 hours. Give the change the student would need to make to the contents of the apparatus and describe how he could calculate the volume of carbon dioxide produced. (3) [2022]

Answer 9

• remove KOH
• record distance liquid moves without KOH
• use difference in distance liquid moves with KOH and without