MCQs / Biology / A Level Biology: Photosynthesis

A Level Biology: Photosynthesis MCQs — Biology

26 multiple-choice questions on A Level Biology: Photosynthesis from Biology, each with the correct answer and, where available, a teacher's explanation. Read through them to revise the chapter, then practise the same questions one by one to test yourself.

1. The light-dependent stage takes place in the

  1. cytoplasm
  2. mitochondrial matrix
  3. stroma
  4. thylakoids

Answer: D) thylakoids

Explanation: Thylakoid membranes hold photosystems. AS & A Level Biology · Topic 13 Photosynthesis · 13.1 Photosynthesis as an energy transfer process

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2. When CO₂ concentration falls, RuBP

  1. decreases
  2. is converted to GP faster
  3. becomes glucose
  4. accumulates because it is not being fixed

Answer: D) accumulates because it is not being fixed

Explanation: Less fixation means RuBP builds up. AS & A Level Biology · Topic 13 Photosynthesis · 13.2 Investigation of limiting factors

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3. GP is reduced to triose phosphate using

  1. water
  2. oxygen
  3. CO₂
  4. reduced NADP and ATP

Answer: D) reduced NADP and ATP

Explanation: Reduction needs reduced NADP and ATP. AS & A Level Biology · Topic 13 Photosynthesis · 13.1 Photosynthesis as an energy transfer process

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4. Chloroplasts are isolated in an ice-cold, isotonic buffer to

  1. kill the chloroplasts
  2. increase photosynthesis
  3. remove chlorophyll
  4. reduce enzyme activity and prevent osmotic damage

Answer: D) reduce enzyme activity and prevent osmotic damage

Explanation: Cold, isotonic and buffered. AS & A Level Biology · Topic 13 Photosynthesis · 13.2 Investigation of limiting factors

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5. Most triose phosphate in the Calvin cycle is used to

  1. make chlorophyll
  2. make NADP
  3. make oxygen
  4. regenerate RuBP

Answer: D) regenerate RuBP

Explanation: Five of six TP regenerate RuBP. AS & A Level Biology · Topic 13 Photosynthesis · 13.1 Photosynthesis as an energy transfer process

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6. Chlorophyll absorbs mainly

  1. green light
  2. red and blue light
  3. ultraviolet only
  4. infrared

Answer: B) red and blue light

Explanation: Green is reflected. AS & A Level Biology · Topic 13 Photosynthesis · 13.1 Photosynthesis as an energy transfer process

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7. In a photosynthesis experiment with pondweed, light intensity is varied by

  1. adding sodium hydrogencarbonate
  2. changing the distance of the lamp
  3. changing the temperature
  4. changing the plant

Answer: B) changing the distance of the lamp

Explanation: Intensity ∝ 1/d². AS & A Level Biology · Topic 13 Photosynthesis · 13.2 Investigation of limiting factors

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8. If the lamp is moved from 10 cm to 20 cm away, light intensity becomes

  1. the same
  2. one quarter
  3. double
  4. half

Answer: B) one quarter

Explanation: Inverse square law. AS & A Level Biology · Topic 13 Photosynthesis · 13.2 Investigation of limiting factors

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9. DCPIP turns colourless in a chloroplast suspension because it

  1. accepts electrons in place of NADP
  2. is broken down by heat
  3. absorbs CO₂
  4. releases oxygen

Answer: A) accepts electrons in place of NADP

Explanation: DCPIP is reduced (Hill reaction). AS & A Level Biology · Topic 13 Photosynthesis · 13.2 Investigation of limiting factors

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10. An action spectrum shows

  1. the rate of photosynthesis at different wavelengths
  2. the structure of chloroplasts
  3. the absorption of each pigment
  4. the Rf values

Answer: A) the rate of photosynthesis at different wavelengths

Explanation: Action = rate. AS & A Level Biology · Topic 13 Photosynthesis · 13.1 Photosynthesis as an energy transfer process

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11. Temperature affects photosynthesis mainly by affecting

  1. the enzymes of the Calvin cycle
  2. the number of chloroplasts
  3. photolysis
  4. the absorption of light

Answer: A) the enzymes of the Calvin cycle

Explanation: Rubisco and other enzymes are temperature-sensitive. AS & A Level Biology · Topic 13 Photosynthesis · 13.2 Investigation of limiting factors

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12. The products of the light-dependent stage used in the Calvin cycle are

  1. CO₂ and water
  2. ATP and reduced NADP
  3. glucose and oxygen
  4. RuBP and GP

Answer: B) ATP and reduced NADP

Explanation: These power carbon fixation. AS & A Level Biology · Topic 13 Photosynthesis · 13.1 Photosynthesis as an energy transfer process

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13. When light intensity is reduced, the concentration of GP

  1. increases because it is not reduced to TP
  2. falls to zero immediately
  3. stays the same
  4. decreases

Answer: A) increases because it is not reduced to TP

Explanation: Less ATP/reduced NADP to convert GP. AS & A Level Biology · Topic 13 Photosynthesis · 13.2 Investigation of limiting factors

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14. In non-cyclic photophosphorylation, electrons lost from PSII are replaced by

  1. electrons from PSI
  2. ATP
  3. electrons from photolysis of water
  4. electrons from NADP

Answer: C) electrons from photolysis of water

Explanation: Water is the electron source. AS & A Level Biology · Topic 13 Photosynthesis · 13.1 Photosynthesis as an energy transfer process

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15. Sodium hydrogencarbonate is added to water around pondweed to

  1. supply carbon dioxide
  2. supply oxygen
  3. provide light
  4. keep the pH low

Answer: A) supply carbon dioxide

Explanation: It releases CO₂. AS & A Level Biology · Topic 13 Photosynthesis · 13.2 Investigation of limiting factors

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16. Which pigment is found in the reaction centre?

  1. Chlorophyll b
  2. Xanthophyll
  3. Chlorophyll a
  4. Carotene

Answer: C) Chlorophyll a

Explanation: Chlorophyll a is the primary pigment. AS & A Level Biology · Topic 13 Photosynthesis · 13.1 Photosynthesis as an energy transfer process

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17. Photolysis of water produces

  1. glucose
  2. ATP and NADP
  3. carbon dioxide
  4. hydrogen ions, electrons and oxygen

Answer: D) hydrogen ions, electrons and oxygen

Explanation: 2H₂O → 4H⁺ + 4e⁻ + O₂. AS & A Level Biology · Topic 13 Photosynthesis · 13.1 Photosynthesis as an energy transfer process

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18. Cyclic photophosphorylation produces

  1. oxygen
  2. reduced NADP only
  3. ATP only
  4. ATP and reduced NADP

Answer: C) ATP only

Explanation: Only PSI; electrons return to PSI. AS & A Level Biology · Topic 13 Photosynthesis · 13.1 Photosynthesis as an energy transfer process

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19. On a graph of rate against light intensity, the plateau at high light shows that

  1. light is limiting
  2. the plant has died
  3. another factor, such as CO₂, is now limiting
  4. photosynthesis has stopped

Answer: C) another factor, such as CO₂, is now limiting

Explanation: A different factor limits. AS & A Level Biology · Topic 13 Photosynthesis · 13.2 Investigation of limiting factors

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20. A limiting factor is

  1. always temperature
  2. the factor in greatest supply
  3. the factor in shortest supply that limits the rate
  4. always light intensity

Answer: C) the factor in shortest supply that limits the rate

Explanation: Definition. AS & A Level Biology · Topic 13 Photosynthesis · 13.2 Investigation of limiting factors

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21. The product of carbon fixation is

  1. triose phosphate
  2. RuBP
  3. glucose
  4. two molecules of glycerate 3-phosphate (GP)

Answer: D) two molecules of glycerate 3-phosphate (GP)

Explanation: Unstable 6C splits into two GP. AS & A Level Biology · Topic 13 Photosynthesis · 13.1 Photosynthesis as an energy transfer process

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22. Protons are pumped into the thylakoid space using energy from

  1. ATP hydrolysis
  2. electrons passing along the electron transport chain
  3. the Calvin cycle
  4. photolysis only

Answer: B) electrons passing along the electron transport chain

Explanation: ETC energy pumps H⁺. AS & A Level Biology · Topic 13 Photosynthesis · 13.1 Photosynthesis as an energy transfer process

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23. The Calvin cycle takes place in the

  1. stroma
  2. grana
  3. thylakoid membrane
  4. outer membrane

Answer: A) stroma

Explanation: Light-independent reactions in the stroma. AS & A Level Biology · Topic 13 Photosynthesis · 13.1 Photosynthesis as an energy transfer process

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24. Rubisco catalyses the reaction between

  1. CO₂ and RuBP
  2. GP and NADP
  3. TP and ATP
  4. oxygen and glucose

Answer: A) CO₂ and RuBP

Explanation: Carbon fixation. AS & A Level Biology · Topic 13 Photosynthesis · 13.1 Photosynthesis as an energy transfer process

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25. In chromatography, the Rf value is

  1. the wavelength absorbed
  2. distance moved by pigment ÷ distance moved by solvent
  3. pigment colour intensity
  4. distance moved by solvent ÷ pigment

Answer: B) distance moved by pigment ÷ distance moved by solvent

Explanation: Definition of Rf. AS & A Level Biology · Topic 13 Photosynthesis · 13.1 Photosynthesis as an energy transfer process

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