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AQA A Level Biology- Photosynthesis –
Practice Questions With Verified Answers &
Rationales LATEST UPDATE THIS YEAR
AQA A Level Biology: Photosynthesis – Practice Questions
Exam Overview
Board: AQA
Qualification: A Level Biology (7402)
Topic: 3.5.1 Photosynthesis (A Level only)
Question Style: A mix of short-answer, data analysis, and extended response questions, similar
to those found in Paper 1, Paper 2, and the essay paper.
Key Skills Tested: Knowledge of the light-dependent and light-independent reactions, the
structure of chloroplasts, the role of pigments, limiting factors, and practical techniques like
chromatography.
Section 1: Chloroplast Structure and Photosynthetic Pigments
1. The diagram below shows a chloroplast. Identify structures A, B, and C.
A: Granum / Grana (stack of thylakoids)
B: Thylakoid (membrane) / Lamella
C: Stroma
,Page 2 of 175
Rationale: These are the key structural components of a chloroplast. The grana are stacks of
thylakoid membranes where the light-dependent reactions occur. The stroma is the fluid-filled
matrix where the light-independent reactions take place.
2. Suggest why chloroplasts contain several different photosynthetic pigments. (2 marks)
Different pigments absorb different / more wavelengths of light.
This allows a wider / larger range of wavelengths to be absorbed for photosynthesis.
Rationale: Each pigment has a specific absorption spectrum. By having a variety of pigments
(e.g., chlorophyll a, chlorophyll b, carotene), the chloroplast can capture a broader range of light
energy, maximizing the rate of photosynthesis.
3. A student carried out thin layer chromatography. The distance travelled by the solvent was
80 mm. Pigment X travelled 52 mm and Pigment Y travelled 70 mm. Calculate the Rf values
for pigments X and Y.
Pigment X: Rf = = 0.65
Pigment Y: Rf = = 0.875
,Page 3 of 175
Rationale: The Rf value is the ratio of the distance travelled by the pigment to the distance
travelled by the solvent front. It is a constant for a given pigment under specific conditions and
is used to identify it.
4. Using the Rf values calculated above and the table of Rf ranges, identify pigments X and Y.
Pigment X: Chlorophyll a (Rf range 0.64-0.69)
Pigment Y: Carotene (Rf range 0.89-0.95)
Rationale: The calculated Rf values fall within the known ranges for these specific pigments,
allowing for identification. This is a key skill in required practical 7.
Section 2: The Light-Dependent Reaction
5. State the exact location of the light-dependent reactions within a plant cell.
The thylakoid membranes of the chloroplasts.
, Page 4 of 175
Rationale: The light-dependent reactions require the photosynthetic pigments (arranged in
photosystems) and the electron transport chain, all of which are embedded in the thylakoid
membranes.
6. Name and describe the process labelled A, which is the loss of electrons from
chlorophyll. (2 marks)
Process: Photoionisation.
Description: Light energy is absorbed by chlorophyll, which excites electrons, causing them to
be lost from the chlorophyll molecule.
Rationale: Photoionisation is the first step in the light-dependent reaction. The absorption of
light energy "excites" electrons in the chlorophyll molecule, causing them to be emitted and
passed down the electron transport chain.
7. State and explain the source of the electrons that replace those lost at stage A. (2 marks)
Source: Water (H₂O).
AQA A Level Biology- Photosynthesis –
Practice Questions With Verified Answers &
Rationales LATEST UPDATE THIS YEAR
AQA A Level Biology: Photosynthesis – Practice Questions
Exam Overview
Board: AQA
Qualification: A Level Biology (7402)
Topic: 3.5.1 Photosynthesis (A Level only)
Question Style: A mix of short-answer, data analysis, and extended response questions, similar
to those found in Paper 1, Paper 2, and the essay paper.
Key Skills Tested: Knowledge of the light-dependent and light-independent reactions, the
structure of chloroplasts, the role of pigments, limiting factors, and practical techniques like
chromatography.
Section 1: Chloroplast Structure and Photosynthetic Pigments
1. The diagram below shows a chloroplast. Identify structures A, B, and C.
A: Granum / Grana (stack of thylakoids)
B: Thylakoid (membrane) / Lamella
C: Stroma
,Page 2 of 175
Rationale: These are the key structural components of a chloroplast. The grana are stacks of
thylakoid membranes where the light-dependent reactions occur. The stroma is the fluid-filled
matrix where the light-independent reactions take place.
2. Suggest why chloroplasts contain several different photosynthetic pigments. (2 marks)
Different pigments absorb different / more wavelengths of light.
This allows a wider / larger range of wavelengths to be absorbed for photosynthesis.
Rationale: Each pigment has a specific absorption spectrum. By having a variety of pigments
(e.g., chlorophyll a, chlorophyll b, carotene), the chloroplast can capture a broader range of light
energy, maximizing the rate of photosynthesis.
3. A student carried out thin layer chromatography. The distance travelled by the solvent was
80 mm. Pigment X travelled 52 mm and Pigment Y travelled 70 mm. Calculate the Rf values
for pigments X and Y.
Pigment X: Rf = = 0.65
Pigment Y: Rf = = 0.875
,Page 3 of 175
Rationale: The Rf value is the ratio of the distance travelled by the pigment to the distance
travelled by the solvent front. It is a constant for a given pigment under specific conditions and
is used to identify it.
4. Using the Rf values calculated above and the table of Rf ranges, identify pigments X and Y.
Pigment X: Chlorophyll a (Rf range 0.64-0.69)
Pigment Y: Carotene (Rf range 0.89-0.95)
Rationale: The calculated Rf values fall within the known ranges for these specific pigments,
allowing for identification. This is a key skill in required practical 7.
Section 2: The Light-Dependent Reaction
5. State the exact location of the light-dependent reactions within a plant cell.
The thylakoid membranes of the chloroplasts.
, Page 4 of 175
Rationale: The light-dependent reactions require the photosynthetic pigments (arranged in
photosystems) and the electron transport chain, all of which are embedded in the thylakoid
membranes.
6. Name and describe the process labelled A, which is the loss of electrons from
chlorophyll. (2 marks)
Process: Photoionisation.
Description: Light energy is absorbed by chlorophyll, which excites electrons, causing them to
be lost from the chlorophyll molecule.
Rationale: Photoionisation is the first step in the light-dependent reaction. The absorption of
light energy "excites" electrons in the chlorophyll molecule, causing them to be emitted and
passed down the electron transport chain.
7. State and explain the source of the electrons that replace those lost at stage A. (2 marks)
Source: Water (H₂O).
