Respiration

Question 1

Describe the process of glycolysis: (4)

Answer 1

• phosphorylation of glucose using ATP
• oxidation of triose phosphate to pyruvate
• net gain of 2 ATP
• NAD reduced

Question 2

Outline of glycolysis:

Answer 2

• glucose phosphorylated to 2x GP
• GP unstable, so breaks down to 2x triose phosphate
• oxidised to pyruvate via NAD -> NADH
• net gain of 2 ATP
• forms 2 pyruvate

Question 3

importance of o2 in respiration:

Answer 3

• o2 is the final e- acceptor in ETC
• if it didn’t accept e-, then no more e- would move down chain
• H+ wouldn’t be tansported across membrane
• so no gradient for FD for H+ down ATP synthase
• so no ATP made

Question 4

efficiency of respiration in aerobic v anaerobic respiration:

Answer 4

aerobic: one glucose -> 38 ATP molecules
anaerobic: one glucose -> 2 ATP

Question 5

In muscles, pyruvate is converted to lactate during prolonged exercise.
Explain why converting pyruvate to lactate allows the continued production of ATP by anaerobic respiration. (2)

Answer 5

1. Regenerates/produces NAD
   OR
   oxidises reduced NAD;.
2. (So) glycolysis continues;
   (glucose to pyruvate)
   (for oxidising/converting triose phosphate to pyruvate)

Question 6

Products of anaerobic in animals v plants/microbes

Answer 6

• animals: lactate
• plants: ethanol + co2

Question 7

Plants produce ATP in their chloroplasts during photosynthesis. They also produce ATP during respiration. Explain why it is important for plants to produce ATP during respiration in addition to during photosynthesis. (5)

Answer 7

• in dark no light for photosynthesis so no ATP produced
• some tissues can’t photosynthesise so need to prod ATP via respiration
• ATP can’t be stored
• plants use more ATP than they produce via photosynthesis
• ATP needed for active transport

Question 8

Purpose of soda lime in respiration practical:

Answer 8

• to absorb co2 prod. during resp
• so volume of o2 absorbed by maggots can be measured
• v(o2) = surrogate for rate of respiration

v(co2)released=v(o2)absorbed, if co2 not rmved, no movement in manometer

Question 9

Why does apparatus need to be air tight during respirometer practical?

Answer 9

• prevent air entering or leaving
• this would change the volume, and so pressure
• effecting movement of colored liquid

Question 10

Explain why the liquid would move towards the left in the manometer would move towards the experimental tube:

Answer 10

• respiring maggots take in o2 from air in experimental tube
• resp. maggots release same amount of co2 as o2 that they absorb
• co2 absorbed by soda lime
• volume of gas decreases in experimental tube -> causes decrease in pressure
• pressure in exp. tube lower than control tube, so colored liquid moves towards exp. tube