Question 1
What property helps make ATP suitable as the short-term energy currency within cells?
A.
It is insoluble and can form large long-term stores in the cytoplasm.
B.
It is water-soluble and can be rapidly hydrolysed to release usable energy.
C.
It stores genetic information in the sequence of its bases.
D.
It diffuses freely through the hydrophobic core of membranes.
Question 2
What occurs during hydrolysis of ATP in a cell?
A.
Water is added, forming ADP and inorganic phosphate with energy release.
B.
Phosphate is removed from ADP, producing ATP and heat.
C.
ADP and inorganic phosphate are joined using energy.
D.
Adenine is removed from ribose, forming three phosphate groups.
Question 3
Which pair of cellular processes both require ATP as an immediate energy source?
A.
Movement down a concentration gradient and gas exchange in alveoli
B.
Active transport and chromosome movement during cell division
C.
Osmosis and diffusion of oxygen through a membrane
D.
Hydrolysis of ATP and movement of water by osmosis
Question 4
What distinguishes cell respiration from gas exchange?
A.
Cell respiration releases energy from carbon compounds to make ATP; gas exchange moves respiratory gases between an organism and its surroundings.
B.
Cell respiration is diffusion of gases; gas exchange is ATP synthesis in mitochondria.
C.
Cell respiration produces oxygen; gas exchange produces glucose from carbon dioxide.
D.
Cell respiration occurs only in lungs; gas exchange occurs only in mitochondria.
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Question 5
In human anaerobic cell respiration, what substrate type is used and what waste product is formed?
A.
Amino acid is used and water is formed.
B.
Lipid is used and carbon dioxide is formed.
C.
Carbohydrate is used and ethanol is formed.
D.
Carbohydrate is used and lactate is formed.
Question 6
A respiratory substrate loses hydrogen atoms that are accepted by NAD. What happens to the substrate and to NAD?
A.
The substrate is oxidized and NAD is reduced.
B.
Both the substrate and NAD are reduced.
C.
The substrate is reduced and NAD is oxidized.
D.
Both the substrate and NAD are oxidized.
Question 7
What is the net yield of glycolysis from one molecule of glucose?
A.
Two pyruvate, two ATP and two reduced NAD
B.
One pyruvate, four ATP and no reduced NAD
C.
Six carbon dioxide, thirty ATP and two reduced NAD
D.
Two lactate, two ATP and two oxidized NAD
Question 8
Why does anaerobic respiration by yeast make bread dough rise?
A.
Lactate produced by yeast expands when heated in the oven.
B.
Water produced in glycolysis evaporates and inflates the dough.
C.
Oxygen released by yeast is trapped between starch molecules.
D.
Carbon dioxide released during ethanol fermentation becomes trapped as bubbles in the dough.
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Question 9
ATP is used by cells as a short-term energy currency rather than as a long-term energy store.
State the full name of ATP.
[1]
Describe two properties of ATP that make it suitable for distributing energy within cells.
[2]
Question 10
A sample of germinating seeds with a mass of uses of oxygen in . What is the oxygen uptake rate per gram of seeds?
A.
B.
C.
D.
Question 11
What is the role of converting pyruvate to lactate during anaerobic respiration in human muscle?
A.
It transfers acetyl groups to coenzyme A for the Krebs cycle.
B.
It generates most ATP by oxidative phosphorylation.
C.
It regenerates NAD so that glycolysis can continue producing ATP.
D.
It produces the carbon dioxide needed to maintain blood pH.
Question 12
What correctly describes the role of oxaloacetate in the Krebs cycle?
A.
It is the two-carbon group transported into the cycle by coenzyme A.
B.
It is decarboxylated to pyruvate before entering the mitochondrial matrix.
C.
It combines with an acetyl group to form citrate and is regenerated by the cycle.
D.
It accepts electrons from oxygen to form metabolic water.
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Question 13
A poison that prevents ATP production is added to a suspension of living animal cells.
State one cellular process, other than cell respiration, that requires ATP.
[1]
Explain why active transport across membranes would decrease after ATP production is inhibited.
[2]
Question 14
ATP and ADP are interconverted continuously in metabolically active cells.
State the products of ATP hydrolysis.
[1]
Explain why ATP must be resynthesized continuously in living cells.
[2]
Question 15
A student states that humans breathe because breathing is the same process as cell respiration.
Define cell respiration.
[1]
Distinguish between cell respiration and gas exchange.
[2]
Question 16
Many reactions in cell respiration involve the removal of hydrogen from respiratory substrates.
Define oxidation in terms of electrons.
[1]
Explain why removal of hydrogen from a substrate can oxidize the substrate.
[1]
State the role of NAD in these reactions.
[1]
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Question 17
Yeast can respire anaerobically when oxygen is unavailable.
State the final products of anaerobic cell respiration in yeast.
[1]
Explain how anaerobic respiration in yeast regenerates NAD.
[2]
Outline one use of yeast fermentation in baking or brewing.
[1]
Question 18
A researcher measured the ATP pool and the rate of ATP hydrolysis in human skeletal muscle fibres at rest and during a short sprint.
Condition | ATP pool / mmol kg | ATP hydrolysis rate / mmol kg min |
|---|---|---|
Rest | 1.2 | 4.8 |
Short sprint | 1.2 | 48 |
Using the data, calculate how long the ATP pool in sprinting muscle would last if ATP were not resynthesized.
[1]
Explain why ATP is suitable as a short-term energy currency in muscle cells.
[2]
Suggest why ATP concentration remains almost constant during the sprint even though ATP hydrolysis increases greatly.
[1]
Question 19
The diagram shows energy coupling between ATP hydrolysis and a membrane transport protein.
State the products formed when ATP is hydrolysed in the diagram.
[1]
Describe the energy transfer shown during ATP synthesis.
[1]
Explain how phosphorylation of the transport protein can help it do work.
[1]
Question 20
A toxin prevents oxygen from accepting electrons at the end of the mitochondrial electron transport chain. What is the most direct consequence?
A.
The intermembrane space becomes more alkaline as protons are pumped faster.
B.
Glycolysis immediately produces a high yield of ATP in the matrix.
C.
Electron flow stops, proton pumping decreases and ATP synthesis by chemiosmosis falls.
D.
ATP synthase directly reduces oxygen to water using electrons from ADP.
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Question 21
Human skeletal muscle cells can produce ATP by aerobic or anaerobic cell respiration.
Write the word equation for anaerobic cell respiration in humans using glucose as the substrate.
[1]
Distinguish between aerobic and anaerobic cell respiration in humans, using three features.
[3]
Question 22
The diagram summarizes glycolysis.
State where glycolysis occurs in a eukaryotic cell.
[1]
Outline the roles of phosphorylation and lysis in glycolysis.
[2]
State the net products of glycolysis from one glucose molecule.
[1]
Question 23
During short periods of intense exercise, oxygen supply to some muscle fibres may be insufficient for aerobic respiration.
State the waste product of anaerobic cell respiration in human muscle fibres.
[1]
Explain how conversion of pyruvate to lactate allows ATP production to continue when oxygen is limited.
[2]
Question 24
Cultured epithelial cells were treated with different inhibitors. The total rate of ATP use and the rate of oxygen uptake were then measured.
Identify the cell process that accounts for the greatest proportion of ATP use in these cells.
[1]
Explain how ATP supplies energy for active transport.
[2]
Suggest why oxygen uptake decreases when ATP use by the cells is reduced.
[1]
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Question 25
Students compared measurements from a small aquatic animal and from isolated cells taken from the same species.
Measurement | 0 min | 20 min |
|---|---|---|
Animal chamber dissolved / mg L | 8.1 | 6.7 |
Animal chamber dissolved / mg L | 0.35 | 1.05 |
Ventilation rate / min | 18 | 31 |
Isolated cells ATP concentration / arbitrary units | 4.0 | 4.1 |
Identify one measurement that provides evidence for cell respiration in the isolated cells.
[1]
Distinguish between gas exchange and cell respiration using the data.
[2]
Suggest why ventilation movements are not a direct measure of the rate of cell respiration.
[1]
Question 26
A dehydrogenase enzyme was extracted from mitochondria. The formation of reduced NAD was monitored using absorbance at after adding respiratory substrate and NAD.
Identify when the rate of NAD reduction is greatest.
[1]
Explain why formation of reduced NAD indicates oxidation of the respiratory substrate.
[2]
Suggest why absorbance stops increasing after the inhibitor is added.
[1]
Question 27
Yeast suspensions were incubated with glucose under aerobic and anaerobic conditions. Carbon dioxide production, ethanol concentration and dough height were measured.
Time / min | (aerobic) / mL | (anaerobic) / mL | Ethanol (aerobic) / | Ethanol (anaerobic) / | Dough height (aerobic) / cm | Dough height (anaerobic) / cm |
|---|---|---|---|---|---|---|
0 | 0 | 0 | 0.0 | 0.0 | 1.0 | 1.0 |
15 | 2 | 8 | 0.0 | 1.0 | 1.1 | 1.5 |
30 | 4 | 16 | 0.0 | 2.0 | 1.1 | 2.1 |
45 | 6 | 24 | 0.0 | 3.0 | 1.2 | 2.7 |
60 | 8 | 24 | 0.0 | 3.0 | 1.2 | 2.7 |
Identify the condition that would be most effective for causing bread dough to rise.
[1]
Compare anaerobic respiration in yeast with anaerobic respiration in human muscle cells.
[2]
Suggest why carbon dioxide production eventually levels off in the anaerobic yeast culture.
[1]
Question 28
A respirometer was used to estimate the rate of aerobic respiration in germinating seeds. The carbon dioxide absorber was placed in the sealed tube. In one trial, the fluid marker moved towards the seeds in . The capillary tube had a cross-sectional area of .
State the role of the carbon dioxide absorber in the respirometer.
[1]
Calculate the rate of oxygen uptake in this trial.
[2]
Suggest one reason for using a matched control tube without respiring seeds.
[1]
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Question 29
Pyruvate produced by glycolysis can enter mitochondria and be processed before the Krebs cycle.
State the cellular location of the link reaction in eukaryotes.
[1]
Outline the conversion of pyruvate to acetyl-CoA in the link reaction.
[2]
State why the Krebs cycle is described as a cycle.
[1]
Question 30
The inner mitochondrial membrane contains electron transport chains and ATP synthase. Oxygen concentration in the surrounding tissue falls during severe oxygen deprivation.
State the role of oxygen in aerobic cell respiration.
[1]
Explain how electron flow in the electron transport chain leads to ATP synthesis.
[3]
Question 31
Blood lactate concentration and oxygen uptake were measured in an athlete during rest, high-intensity exercise and recovery.
Describe the change in blood lactate concentration during high-intensity exercise.
[1]
Compare aerobic and anaerobic respiration in human muscle cells.
[2]
Explain why oxygen uptake remains elevated during recovery after the exercise has ended.
[2]
Question 32
A respirometer was used to measure oxygen uptake by germinating seeds. Potassium hydroxide solution was placed in the chamber and a matched control tube contained glass beads instead of seeds.
Tube | Marker movement / mm | Time / min | Sample mass / g | Capillary area / |
|---|---|---|---|---|
Germinating seeds | 18 | 10 | 0.50 | 0.020 |
Control (glass beads) | 4 | 10 | 0.50 | 0.020 |
Calculate the corrected oxygen uptake rate per gram of seeds.
[2]
Outline the purpose of the potassium hydroxide solution.
[1]
Suggest two variables, other than mass of seeds, that should be controlled in this investigation.
[2]
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Question 33
The main events in glycolysis were investigated in a cell-free cytoplasm extract supplied with glucose, ADP, phosphate and NAD.
Event | Uninhibited extract / molecules per glucose | Inhibited extract / molecules per glucose |
|---|---|---|
ATP produced | 4 | 2 |
ATP used | 2 | 1 |
Reduced NAD formed | 2 | 1 |
Pyruvate formed | 2 | 1 |
Calculate the net yield of ATP per glucose molecule in the uninhibited extract.
[1]
Explain why each event after lysis occurs twice per glucose molecule.
[1]
Using the data, outline the roles of oxidation and ATP formation in glycolysis.
[2]
Suggest why inhibiting the first phosphorylation step decreases pyruvate formation even though less ATP is used.
[1]
Question 34
Human muscle cells were incubated without oxygen. Some cultures were treated with an inhibitor of lactate dehydrogenase, the enzyme that converts pyruvate to lactate.
Describe the effect of the lactate dehydrogenase inhibitor on lactate formation and ATP production.
[1]
Explain how conversion of pyruvate to lactate allows anaerobic respiration to continue in human muscle.
[2]
Calculate the ATP produced when of glucose is metabolized anaerobically by these muscle cells.
[1]
Question 35
ATP is continually hydrolysed and resynthesized in living cells. A student stated that ATP is useful because it stores most of the cell's energy for long periods.
Explain why ATP is described as a nucleotide and as an energy currency.
[3]
A cell in which ATP synthesis has stopped continues to hydrolyse ATP for a short time.
I.
State the products of ATP hydrolysis.
[1]
II.
Discuss two consequences for cellular processes if ATP is not regenerated.
[2]
Question 36
A student wrote: "Breathing is cell respiration because both involve oxygen and carbon dioxide."
Discuss the student's statement by distinguishing gas exchange from cell respiration.
[4]
Cells can use different respiratory substrates.
I.
State two examples of respiratory substrates used by cells.
[1]
II.
Explain why the oxidation of substrates in cell respiration occurs in a series of steps.
[2]
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Question 37
Cells in a root hair actively absorb mineral ions and also synthesize proteins needed for growth.
Explain the role of ATP in active transport across the root hair cell membrane.
[3]
Protein synthesis and cell growth require ATP.
I.
State the type of metabolism that builds larger molecules from smaller molecules.
[1]
II.
Explain why ATP is required for protein synthesis and movement of cell components during growth.
[2]
Question 38
The diagram summarizes the link reaction and the Krebs cycle in a mitochondrion. Carbon atoms in intermediates are indicated.
State where the link reaction and Krebs cycle occur in a eukaryotic cell.
[1]
Using the diagram, explain why the link reaction is described as both decarboxylation and oxidation.
[2]
Calculate the number of carbon dioxide molecules released by the link reaction and Krebs cycle for each glucose molecule fully respired aerobically.
[1]
Explain why oxaloacetate is not used up by the Krebs cycle.
[1]
Question 39
Isolated mitochondria were supplied with ADP, inorganic phosphate and different respiratory substrates. Some treatments lacked oxygen or contained a compound that makes the inner mitochondrial membrane permeable to protons.
Substrate | present? | leak? | consumption / a.u. | ATP synthesis / a.u. |
|---|---|---|---|---|
Carbohydrate | Yes | No | 12 | 6 |
Carbohydrate | No | No | 0 | 0 |
Carbohydrate | Yes | Yes | 15 | 1 |
Lipid | Yes | No | 20 | 14 |
Lipid | No | No | 0 | 0 |
Lipid | Yes | Yes | 24 | 1 |
Explain the effect of removing oxygen on electron transport and ATP synthesis.
[2]
Explain why the proton-permeable compound decreases ATP synthesis even when electron transport continues.
[2]
Using the substrate data, evaluate one advantage and one limitation of lipids as respiratory substrates compared with carbohydrates.
[1]
Question 40
During a repeated sprint test, oxygen uptake, ATP demand and blood lactate concentration were measured in a group of trained athletes.
Compare aerobic and anaerobic respiration in human cells.
[4]
Use the data to explain why lactate concentration changes during and after the sprint period.
I.
Explain why lactate concentration increases during the sprints.
[2]
II.
Suggest why oxygen uptake remains high during recovery.
[2]
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Question 41
A respirometer was used to estimate oxygen uptake by germinating seeds at different temperatures. Carbon dioxide was absorbed by potassium hydroxide and movement of a fluid marker was recorded.
Explain why movement of the fluid marker can be used to estimate the rate of aerobic respiration.
[3]
The capillary tube was calibrated so that marker distance could be converted to gas volume.
I.
Calculate the corrected respiration rate per gram of seeds using the table.
[2]
II.
Identify the independent variable in this investigation.
[1]
Evaluate two features of the experimental design that improve the validity or reliability of the results.
[2]
Question 42
A student investigated the effect of temperature on the rate of respiration in small invertebrates using oxygen uptake as the dependent variable.
Explain why oxygen uptake can be used to estimate respiration rate in this investigation.
[2]
Use the graph to analyse the effect of temperature on respiration rate.
I.
Describe the trend shown over the tested temperature range.
[1]
II.
Explain why this trend should not be extrapolated indefinitely to higher temperatures.
[2]
Evaluate three variables, other than temperature, that should be controlled to make the comparison valid.
[3]
Question 43
Muscle cells can continue to produce some ATP during short periods when oxygen supply is insufficient. This depends on reactions involving NAD, pyruvate and lactate.
Explain the role of NAD in oxidation reactions during cell respiration.
[3]
Glycolysis converts glucose to pyruvate in the cytoplasm.
I.
Outline the sequence of events in glycolysis without naming the intermediates.
[2]
II.
State the net products of glycolysis per glucose molecule relevant to respiration.
[1]
Explain why conversion of pyruvate to lactate allows glycolysis to continue when oxygen is insufficient.
[2]
Question 44
The diagram summarizes the entry of carbon from glucose into the aerobic stages of respiration in a mitochondrion.
Explain the link reaction in aerobic respiration.
[3]
The acetyl group enters the Krebs cycle.
I.
Describe how citrate is formed and why the Krebs pathway is a cycle.
[2]
II.
State the main products of one turn of the Krebs cycle.
[1]
Compare the link reaction and the Krebs cycle with respect to oxidation and decarboxylation.
[2]
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Question 45
Yeast cells were grown in sealed flasks containing glucose solution. Carbon dioxide production and ethanol concentration were measured and compared with lactate production in human muscle cells during intense exercise.
Compare anaerobic respiration in yeast and in human muscle cells.
[3]
In yeast, pyruvate is converted to ethanol and carbon dioxide.
I.
Outline how NAD is regenerated in yeast fermentation.
[1]
II.
Explain why carbon dioxide production can be used as evidence for yeast fermentation.
[1]
Discuss how the products of yeast anaerobic respiration are used in baking and brewing.
[2]
Question 46
An endurance athlete changed from a high-carbohydrate meal before training to a high-fat meal of equal mass. The athlete then performed a short maximal sprint followed by prolonged low-intensity exercise.
Exercise bout | Meal type | ATP from carbohydrate / rel. units | ATP from lipid / rel. units |
|---|---|---|---|
Sprint | High-carb meal | 90 | 5 |
Sprint | High-fat meal | 60 | 2 |
Low-intensity | High-carb meal | 30 | 50 |
Low-intensity | High-fat meal | 15 | 85 |
Compare carbohydrates and lipids as respiratory substrates.
[4]
Use the information to evaluate which meal would better support each type of exercise.
I.
Suggest which substrate is most useful during the short maximal sprint.
[2]
II.
Suggest which substrate is most useful during prolonged low-intensity exercise and justify your answer.
[2]
Question 47
Isolated mitochondria were supplied with pyruvate, ADP and phosphate. Scientists then added either an electron transport inhibitor or a compound that makes the inner mitochondrial membrane permeable to protons.
Time / min | (control) / % initial | (+ inhibitor) / % initial | (+ uncoupler) / % initial | Proton gradient (control) / a.u. | Proton gradient (+ inhibitor) / a.u. | Proton gradient (+ uncoupler) / a.u. | ATP (control) / a.u. | ATP (+ inhibitor) / a.u. | ATP (+ uncoupler) / a.u. |
|---|---|---|---|---|---|---|---|---|---|
0 | 100 | 100 | 100 | 0 | 0 | 0 | 0 | 0 | 0 |
2 | 88 | 88 | 88 | 25 | 25 | 25 | 12 | 12 | 12 |
4* | 76 | 76 | 76 | 50 | 50 | 50 | 24 | 24 | 24 |
6 | 64 | 75 | 58 | 50 | 15 | 8 | 36 | 24 | 26 |
8 | 52 | 75 | 40 | 50 | 5 | 0 | 48 | 24 | 27 |
Explain how reduced NAD transfers energy to the electron transport chain.
[2]
Electron flow along the chain is coupled to ATP synthesis.
I.
Explain how the proton gradient is generated.
[2]
II.
Explain how chemiosmosis produces ATP.
[2]
Use the data to evaluate the effects of the two treatments on aerobic respiration.
[2]
Question 48
A mutation reduces the amount of functional ATP synthase in the inner mitochondrial membrane of liver cells. The cells are supplied with glucose and oxygen.
Explain the role of oxygen in aerobic respiration.
[3]
ATP synthase is reduced but the electron transport chain remains present.
I.
Predict the effect of reduced ATP synthase on the proton gradient and ATP production.
[2]
II.
State the location of ATP synthase in mitochondria.
[1]
Evaluate how the mutation could affect earlier stages of aerobic respiration.
[2]
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