ATP - AQA A-Level Biology (Paper 1) Exam Questions

Practise 17 exam-style questions on ATP for AQA A-Level Biology (Paper 1). Write your answer as you would in the exam and get it marked in seconds against the mark scheme, point by point, with the Study Helper on hand if you get stuck.

17 questions
1–8 marks each
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17 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

2 marks

ATP is described as a nucleotide derivative.

Give one similarity and one difference between the structure of a molecule of ATP and the structure of an RNA nucleotide that contains adenine.

Model answer

Similarity: both contain ribose (and adenine).
Difference: ATP has three phosphate groups, but the RNA nucleotide has only one phosphate group.

Explanation

An RNA nucleotide containing adenine is adenine + ribose + one phosphate group. ATP has the same adenine and ribose but three phosphate groups, which is why it is called a nucleotide derivative. Make sure each answer compares the two molecules; do not say ATP contains deoxyribose.

Mark scheme

1 mark
Similarity: both contain ribose / adenine / a phosphate group
List rule: if more than one similarity is given, a wrong one (e.g. 'both contain deoxyribose') cancels the correct one. Accept 'both contain a pentose and a base' only if named as ribose and adenine.
1 mark
Difference: ATP has three phosphate groups but the RNA nucleotide has one
Accept 'ATP has two more phosphate groups' or 'ATP has more phosphate groups than the nucleotide'. List rule applies. Do not accept differences in the sugar or the base.

Question 2

3 marks

In cells, the amino acid glutamine is made from another amino acid, glutamate, and ammonia. This reaction requires energy. It is catalysed by one enzyme in two steps:
- step 1: a phosphate group is transferred from ATP to glutamate, forming ADP and glutamyl phosphate
- step 2: ammonia reacts with glutamyl phosphate, forming glutamine and inorganic phosphate (Pi).

Use this information and your knowledge of ATP to explain how the hydrolysis of ATP enables glutamine to be made.

Model answer

The hydrolysis of ATP releases energy, and this energy-releasing reaction is coupled to the energy-requiring formation of glutamine. The phosphate group from ATP phosphorylates glutamate, forming glutamyl phosphate. This makes the glutamate more reactive, lowering the activation energy for its reaction with ammonia, so glutamine can form.

Explanation

ATP hydrolysis can be coupled to energy-requiring reactions, and the phosphate released can phosphorylate other compounds, often making them more reactive. Here the phosphate is passed to glutamate and then released as Pi in step 2, so the overall result is ATP → ADP + Pi with glutamine made. Say that ATP 'releases' energy, never that it 'produces' energy.

Mark scheme

1 mark
(Hydrolysis of) ATP releases energy, which is used for the (energy-requiring) reaction / the two reactions are coupled
Reject 'ATP produces / makes / creates energy'.
1 mark
The phosphate (from ATP) phosphorylates glutamate / glutamate is phosphorylated
Accept 'a phosphate group is added to glutamate (forming glutamyl phosphate)'.
1 mark
(Phosphorylation) makes glutamate more reactive / lowers the activation energy for its reaction with ammonia
Accept 'glutamyl phosphate reacts more easily with ammonia'. Ignore 'provides energy' unqualified.

Question 3

3 marks

The hydrolysis of 1 mol of ATP releases 30.5 kJ of energy. One mole contains 6.02 × 10²³ molecules.

A carrier protein moves calcium ions out of a cell against their concentration gradient. Moving one calcium ion needs at least 2.2 × 10⁻²⁰ J of energy.

Calculate the energy, in J, released by the hydrolysis of one molecule of ATP. Give your answer in standard form.

Use your answer to calculate the maximum number of calcium ions that could be moved for each molecule of ATP hydrolysed.

Model answer

Energy per molecule = 30.5 kJ ÷ 6.02 × 10²³ = 30 500 J ÷ 6.02 × 10²³ = 5.07 × 10⁻²⁰ J
Calcium ions per ATP = 5.07 × 10⁻²⁰ ÷ 2.2 × 10⁻²⁰ = 2.3
A whole number of ions must be moved, so the maximum is 2 calcium ions.

Explanation

Convert kJ to J (× 1000) before dividing by the number of molecules in a mole. The energy from one ATP is enough for two calcium ions but not three, so you must round down. This shows why ATP is useful: each molecule releases a small, manageable amount of energy that matches the needs of individual reactions.

Mark scheme

1 mark
Correct method: 30 500 ÷ 6.02 × 10²³; or a correct final answer of 5.07 × 10⁻²⁰ (J) with no working
A correct answer in the range 5.0 × 10⁻²⁰ to 5.1 × 10⁻²⁰ J with no working scores 2 marks (points 1 and 2). Accept for 1 mark: 5.07 × 10⁻²³ (kJ not converted to J) OR a correct value that is not in standard form.
1 mark
5.07 × 10⁻²⁰ (J)
Accept 5.0 × 10⁻²⁰ to 5.1 × 10⁻²⁰ (e.g. 5.1 × 10⁻²⁰, 5.066 × 10⁻²⁰).
1 mark
2 (calcium ions)
Do not accept 2.3 (a fraction of an ion cannot be moved) or 3. ECF: accept the whole number, rounded down, from (their energy per molecule) ÷ 2.2 × 10⁻²⁰.

Question 4

5 marks

A student wrote: "A glucose molecule contains much more energy than an ATP molecule, so it would be better for cells to use glucose directly as the source of energy for processes such as active transport."

Use your knowledge of ATP to explain why cells use ATP, not glucose, as the immediate source of energy for these processes.

Model answer

Although a glucose molecule contains more energy, it is not suitable as an immediate source of energy. ATP is hydrolysed in a single reaction, catalysed by ATP hydrolase, so energy is released immediately, whereas glucose releases its energy only through the many reactions of respiration. The hydrolysis of one ATP molecule releases a small, manageable amount of energy, so little is wasted as heat; oxidising a glucose molecule releases far more energy than any one reaction needs. ATP is rapidly resynthesised from ADP and Pi, so it is continually available. The phosphate released can phosphorylate other compounds, making them more reactive. ATP is also small and soluble, so it moves easily to where energy is needed, and it cannot leave the cell.

Explanation

Glucose stores more energy per molecule, but this is a disadvantage for an immediate energy source: it releases its energy only through the many reactions of respiration, and releasing it all at once would waste most of it as heat. ATP is hydrolysed in a single reaction, releasing a small, manageable amount of energy, and it is rapidly resynthesised. Good answers compare ATP with glucose and give properties of ATP itself; avoid saying ATP 'produces energy' or 'stores large amounts of energy'.

Mark scheme

1 mark
ATP is hydrolysed in a single reaction / by one enzyme, so energy is released quickly / immediately
Max 5.
1 mark
Glucose releases energy only through many reactions / steps (in respiration), so (more) slowly
1 mark
Hydrolysis of ATP releases a small / manageable amount of energy (at a time)
Accept 'glucose would release too much energy at once'.
1 mark
So little energy is wasted / lost as heat
Accept 'cells are not damaged by overheating'.
1 mark
ATP is rapidly resynthesised (from ADP and Pi)
1 mark
The (inorganic) phosphate from ATP can phosphorylate other compounds, making them more reactive
1 mark
ATP is small / soluble, so it moves easily within the cell (to where energy is needed)
1 mark
ATP cannot leave the cell / does not pass through the cell-surface membrane
Accept 'is not lost from the cell'.

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