RespirationAQA A-Level Biology: Topic test

20 questions, 54 marks

AQA A-Level Biology

Respiration topic test

Total 54 marks

Name

Class

Date

1
Mature human red blood cells contain no mitochondria. They take up glucose from the blood plasma, produce ATP, and release lactate into the plasma.
(a)
Which stage of glycolysis uses ATP?
[1 mark]
AOxidation of triose phosphate to pyruvate
BConversion of pyruvate to lactate
CPhosphorylation of glucose to glucose phosphate
DProduction of reduced NAD
(b)
What is the main benefit to a red blood cell of converting pyruvate to lactate?
[1 mark]
AIt regenerates NAD so that glycolysis can continue.
BIt produces extra ATP by substrate-level phosphorylation.
CIt allows pyruvate to enter the Krebs cycle.
DIt removes oxygen from the cell.
(c)
Glycolysis uses ATP in its first stage, yet it gives a net gain of ATP. Explain why.
[2 marks]
Total for question 1: 4 marks
2
Acetylcoenzyme A is formed in the matrix of the mitochondria of a liver cell and enters the Krebs cycle.
(a)
What happens when acetylcoenzyme A enters the Krebs cycle?
[1 mark]
AIt combines with pyruvate and releases carbon dioxide.
BIt is hydrolysed to acetate and glucose.
CIt is reduced to form a four-carbon compound.
DIt reacts with a four-carbon compound, releasing coenzyme A and forming a six-carbon compound.
(b)
What happens to the reduced NAD produced in the Krebs cycle?
[1 mark]
AIt is used in glycolysis to oxidise triose phosphate.
BIt donates electrons to the electron transfer chain on the inner mitochondrial membrane and becomes NAD.
CIt is hydrolysed to release the energy that makes ATP directly.
DIt combines with acetate to form acetylcoenzyme A.
(c)
State two products of the Krebs cycle, other than ATP, that are formed in the matrix.
[2 marks]
Total for question 2: 4 marks
3
A student investigated the effect of glucose concentration on the rate of respiration of a culture of aerobic bacteria. The culture was well aerated and kept at 30 °C. At each glucose concentration, the volume of oxygen taken up in 10 minutes was measured. The volumes were 1.2 cm³ at 0.5% glucose, 2.4 cm³ at 1.0%, 4.1 cm³ at 2.0% and 4.3 cm³ at 4.0%.
(a)
Calculate the percentage increase in the rate of oxygen uptake when the glucose concentration is raised from 1.0% to 2.0%. Give your answer to two significant figures.
[3 marks]
(b)
Explain why oxygen is needed by the bacteria for this respiration, and suggest why the rate of oxygen uptake hardly increased when the glucose concentration was raised from 2.0% to 4.0%.
[4 marks]
Total for question 3: 7 marks
4
During a fast lasting several days, a woman's stores of glycogen are used up. Her cells then rely increasingly on fatty acids from stored lipids and amino acids from protein as respiratory substrates.
(a)
Describe how fatty acids and amino acids can be used to produce ATP by aerobic respiration.
[6 marks]
(b)
Explain why the respiration of fatty acids stops in cells that have no oxygen, whereas cells can still make some ATP from glucose.
[6 marks]
Total for question 4: 12 marks
5
The roots of a rice plant are in waterlogged soil with no oxygen. The root cells convert pyruvate to ethanol.
(a)
What is the function of converting pyruvate to ethanol in these root cells?
[1 mark]
AIt produces ATP by oxidative phosphorylation.
BIt oxidises reduced NAD to NAD, so that glycolysis can continue.
CIt provides acetylcoenzyme A for the Krebs cycle.
DIt phosphorylates glucose.
(b)
What are the net products of glycolysis for each glucose molecule?
[1 mark]
A2 ATP, 2 reduced NAD and 2 pyruvate
B4 ATP, 2 reduced NAD and 2 pyruvate
C2 ATP, 2 reduced NAD and 1 pyruvate
D32 ATP, 10 reduced NAD and 2 pyruvate
(c)
Explain why the root cells make much less ATP for each glucose molecule than they would if oxygen were present.
[2 marks]
Total for question 5: 4 marks
6
A cell biologist compares mitochondria from a liver cell and from a flight muscle cell of a bird. The flight muscle mitochondria have a much more extensively folded inner membrane.
(a)
How does the extensive folding of the inner membrane increase the rate of ATP production?
[1 mark]
AIt increases the volume of the matrix for glycolysis.
BIt allows oxygen to be made in the membrane.
CIt provides a larger surface area for electron transfer chains and ATP synthase.
DIt prevents protons passing into the matrix.
(b)
Which stages of aerobic respiration take place in the matrix of the mitochondrion?
[1 mark]
AGlycolysis
BOxidative phosphorylation
CThe Krebs cycle only
DThe link reaction and the Krebs cycle
(c)
Explain how the movement of protons through ATP synthase leads to the production of ATP.
[2 marks]
Total for question 6: 4 marks
7
Lactic acid bacteria in a fermenter have no oxygen. They use 0.45 mol of glucose per hour, and convert all the pyruvate formed into lactate.
(a)
Calculate the amount, in mol, of net ATP produced per hour by glycolysis and the amount of reduced NAD re-oxidised per hour by lactate formation.
[3 marks]
(b)
Explain why the ATP yield from each glucose molecule is much lower in these bacteria than in an aerobic cell.
[4 marks]
Total for question 7: 7 marks
8
During a heart attack, a blocked coronary artery leaves part of the heart muscle with very little oxygen. The affected cells switch to anaerobic respiration and the lactate concentration in the area rises.
(a)
Explain why the production of ATP by the mitochondria in these cells falls when oxygen is in short supply.
[6 marks]
(b)
Explain how the formation of lactate allows the heart muscle cells to go on making some ATP, and suggest why the heart muscle cannot rely on this for long.
[6 marks]
Total for question 8: 12 marks

End of questions

Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).