Practise 30 exam-style questions on Metabolism for AQA GCSE Biology. Write your answer as you would in the exam and get it marked in seconds against the mark scheme, point by point, with an AI tutor on hand if you get stuck.
30 questions
3–6 marks each
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20 questions, marked as you go
Sample questions with model answers
Here are 4 of the questions in this topic, each with a model answer, an explanation of why it earns the marks and the mark scheme an examiner would use.
Question 1
3 marks
State the role of ATP in metabolism and give one example of a metabolic process that uses ATP.
Model answer
ATP provides energy for cellular processes by hydrolysis to ADP + Pi. Example: active transport, biosynthesis (protein synthesis), muscle contraction.
Explanation
ATP is the immediate energy currency of the cell. Examples of ATP usage include active transport across membranes and anabolic reactions.
Mark scheme
1 mark
ATP provides energy for cellular processes / metabolism (ATP ? ADP + Pi releases energy)
2 marks
Example e.g., active transport / protein synthesis / muscle contraction
Award 1 mark for naming a metabolic process and 1 for linking to ATP use.
Question 2
4 marks
Explain why a person continues to breathe deeply for some time after finishing intense exercise (oxygen debt).
Model answer
During intense exercise anaerobic respiration produces lactic acid; extra oxygen post-exercise is needed to oxidise lactic acid to CO2 and H2O and to restore oxygen stores in blood and muscle (myoglobin) and to replenish ATP/creatine phosphate.
Explanation
Oxygen debt: extra post-exercise oxygen metabolises accumulated lactic acid, restores oxygen stores and replenishes high-energy compounds. Each correct component earns marks.
Mark scheme
1 mark
Intense exercise leads to anaerobic respiration and lactic acid accumulation
1 mark
Extra oxygen after exercise (oxygen debt) is used to oxidise lactic acid (to CO2 and H2O)
1 mark
Oxygen is also needed to restore oxygen stores in blood and muscle (myoglobin) and to replenish ATP/creatine phosphate
1 mark
Hence breathing remains deep/rapid until recovery processes complete
Question 3
4 marks
Describe how you would calculate the energy transferred by respiration in a food sample using a simple calorimetry experiment with a spirit burner.
Model answer
Burn a known mass of food and use released heat to warm a known mass of water; measure temperature change of water. Energy transferred = mass water × specific heat capacity (4.18 J/g°C) × temperature change divided by mass of food burned (J/g).
Explanation
Method details: control conditions, stir water, insulate, measure mass loss of food, then calculate energy per gram. Award marks for formula and method components.
Mark scheme
1 mark
Measure temperature change of a known mass of water heated by combustion
1 mark
Calculate energy gained by water = mass water × 4.18 J/g°C × ?T
1 mark
Measure mass of food burned to get energy per gram: divide energy by mass burnt (J/g)
1 mark
Include controls: insulation, stirring, avoid heat loss (qualitative) to improve accuracy
Question 4
5 marks
Compare the use of carbohydrates, fats and proteins as respiratory substrates during prolonged exercise when glycogen stores are low.
Model answer
Initially carbohydrates (glucose/glycogen) are primary substrate. During prolonged exercise when glycogen is low, fats (fatty acids) become major substrate via beta-oxidation producing acetyl CoA. Proteins can be used by deamination of amino acids but are a minor source and used when other stores low.
Explanation
Expect ordering and reasons: carbohydrate preferred for rapid ATP, fats for long-term energy (more ATP per g), proteins only catabolised when needed; mention oxygen requirement for fatty acid oxidation.
Mark scheme
2 marks
Carbohydrates are used first (glucose/glycogen) for rapid ATP; when glycogen low fats become main substrate (beta-oxidation ? acetyl CoA)
1 mark
Fats provide more ATP per gram and are used for prolonged energy supply
1 mark
Proteins are used as a minor substrate via deamination when other stores are depleted
1 mark
Fat oxidation requires more oxygen than carbohydrate (so oxygen availability influences substrate choice)
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