Lesson 3.5.2.1

3.5.2.1 Glycolysis, the link reaction and the Krebs cycle Quiz: AQA Biology, Unit 5

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 3.5.2.1, Glycolysis, the link reaction and the Krebs cycle: 20 multiple choice questions for the AQA Biology (7402), Unit 5: Energy transfers in and between organisms, written with Revision Ninja.

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The 20 questions

  1. Where does glycolysis take place?

    • In the thylakoid membranes
    • In the stroma of chloroplasts
    • In the mitochondrial matrix
    • In the cytoplasm

  2. How many molecules of pyruvate are produced from one molecule of glucose in glycolysis?

    • Six
    • Four
    • One
    • Two

  3. What is the net gain of ATP in glycolysis for each glucose molecule?

    • Zero ATP
    • Six ATP
    • Four ATP
    • Two ATP

  4. Which reaction describes the first stage of glycolysis?

    • Reduction of oxygen to water
    • Production of acetyl coenzyme A
    • Phosphorylation of glucose to glucose phosphate, using ATP
    • Oxidation of pyruvate to acetate

  5. In glycolysis, reduced NAD is formed. Which stage produces it?

    • Phosphorylation of glucose
    • Breakdown of ATP to ADP
    • Oxidation of triose phosphate to pyruvate
    • Formation of glucose phosphate

  6. What is the link reaction?

    • Conversion of ATP to ADP in the cytoplasm
    • Movement of electrons along the electron transfer chain
    • Breakdown of glucose to lactate in muscle
    • Conversion of pyruvate to acetate, forming reduced NAD and carbon dioxide, and combining it with coenzyme A

  7. What is produced when acetylcoenzyme A reacts with a four-carbon molecule in the link stage?

    • A three-carbon molecule of pyruvate
    • A six-carbon molecule that enters the Krebs cycle
    • A molecule of ethanol
    • A molecule of glucose

  8. Where does the Krebs cycle take place in aerobic respiration?

    • In the cytoplasm
    • In the thylakoid lumen
    • In the mitochondrial matrix
    • In the inner membrane of the mitochondrion

  9. How does pyruvate enter the mitochondrial matrix in aerobic respiration?

    • Through ATP synthase
    • By active transport
    • By simple diffusion through the outer membrane
    • By osmosis across the cell surface membrane

  10. Which molecule is released as a waste product of the Krebs cycle?

    • Oxygen
    • Lactate
    • Water
    • Carbon dioxide

  11. Per acetylcoenzyme A entering the Krebs cycle, how many molecules of reduced coenzymes are generated, excluding those formed by the link reaction?

    • Six reduced NAD and two reduced FAD
    • Three reduced NAD and one reduced FAD
    • Two reduced NAD and one reduced FAD
    • One reduced NAD and three reduced FAD

  12. For one glucose molecule respired aerobically, how many molecules of carbon dioxide are produced during the link reaction and Krebs cycle combined?

    • Six from the link reaction alone
    • Two from the link reaction and four from the Krebs cycle, totalling six
    • Two in total
    • Four in total

  13. Which molecule is directly produced by substrate-level phosphorylation in the Krebs cycle?

    • ATP
    • Glucose
    • Pyruvate
    • Oxygen

  14. Which substances, other than glucose, can act as respiratory substrates and enter the Krebs cycle?

    • Breakdown products of lipids and amino acids
    • Only products of photosynthesis such as starch
    • Only carbon dioxide and water
    • Only ethanol and lactate

  15. A student says that glycolysis requires oxygen and occurs in the mitochondrion. Which correction is most accurate?

    • Glycolysis is aerobic and takes place in the mitochondrion
    • Glycolysis requires oxygen but takes place in the matrix
    • Glycolysis takes place in the nucleus
    • Glycolysis is anaerobic and takes place in the cytoplasm

  16. Which statement about the link reaction and the Krebs cycle is correct?

    • Neither produces carbon dioxide
    • Both produce ethanol as a by-product
    • Both produce carbon dioxide, and the Krebs cycle generates ATP by substrate-level phosphorylation
    • Both take place in the cytoplasm

  17. A cell has no oxygen. Which of the following stages of aerobic respiration will be unable to continue?

    • Phosphorylation of glucose using ATP
    • The Krebs cycle, because reduced NAD cannot be reoxidised without oxygen in the electron transfer chain
    • Glycolysis, which needs oxygen to split glucose
    • The breakdown of glucose to pyruvate in the cytoplasm

  18. How many ATP molecules are produced by substrate-level phosphorylation in glycolysis for each glucose molecule, before the 2 ATP used at the start are subtracted?

    • 8
    • 6
    • 2
    • 4

  19. Which intermediate is a three-carbon molecule formed during glycolysis?

    • Acetylcoenzyme A
    • Triose phosphate
    • Citrate
    • Ribulose bisphosphate

  20. Which compound is formed when acetate combines with coenzyme A in the link reaction?

    • Glycerate 3-phosphate
    • Acetylcoenzyme A
    • Citrate
    • Pyruvate

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