7.2.3 Link reaction and Krebs cycle Quiz: Pearson Edexcel Biology, Unit 7

The 20 questions

1. What molecule is pyruvate converted into during the link reaction?

   • Lactate
   • Oxaloacetate
   • Acetyl CoA
   • Citrate

2. In which part of the mitochondrion do the link reaction and Krebs cycle occur?

   • Intermembrane space
   • Inner membrane
   • Outer membrane
   • Mitochondrial matrix

3. How many carbon dioxide molecules are released per turn of the Krebs cycle?

   • 3
   • 2
   • 1
   • 4

4. How many reduced NAD molecules are produced per turn of the Krebs cycle?

   • 2
   • 3
   • 4
   • 1

5. How many reduced NAD molecules are produced per glucose during the link reaction and Krebs cycle combined?

   • 10
   • 8
   • 2
   • 6

6. Why does the Krebs cycle stop when oxygen is absent?

   • Enzymes denatured
   • Glucose depleted
   • ATP accumulated
   • Coenzymes unregenerated

7. Which molecule is regenerated at the end of the Krebs cycle to react with acetyl CoA?

   • Succinate
   • Citrate
   • Oxaloacetate
   • Pyruvate

8. What compound is pyruvate converted into during the link reaction?

   • Citrate
   • Oxaloacetate
   • Acetyl CoA
   • Lactate

9. What is the primary yield of the Krebs cycle?

   • Reduced coenzymes
   • ATP molecules
   • Carbon dioxide
   • Acetyl groups

10. Why do the link reaction and Krebs cycle occur inside mitochondria?

    • Membranes absorb light
    • Cristae store electrons
    • Cytoplasm lacks oxygen
    • Matrix contains enzymes

11. Which product is released during the link reaction but NOT during glycolysis?

    • Reduced NAD
    • ATP
    • Carbon dioxide
    • Pyruvate

12. In the first step of the Krebs cycle, acetyl CoA combines with oxaloacetate to form:

    • Lactate
    • Glucose
    • Citrate
    • Pyruvate

13. By what mechanism is ATP directly produced in the Krebs cycle?

    • Chemiosmosis
    • Photophosphorylation
    • Oxidative phosphorylation
    • Substrate-level phosphorylation

14. What effect does a Krebs cycle inhibitor have on mitochondrial carbon dioxide output?

    • Decreased output
    • Increased output
    • Uncontrolled release
    • No change

15. Where do reduced NAD and reduced FAD deliver electrons during respiration?

    • Outer membrane
    • Electron transport chain
    • Mitochondrial matrix
    • Cytoplasm

16. Which stage of aerobic respiration produces the majority of ATP?

    • Link reaction
    • Glycolysis
    • Oxidative phosphorylation
    • Krebs cycle

17. What molecule is released during a decarboxylation reaction in respiration?

    • Pyruvate
    • Oxygen
    • Carbon dioxide
    • Water

18. Why does the Krebs cycle take place specifically within the mitochondrial matrix?

    • Contains required enzymes
    • Contains electron carriers
    • Has high pH
    • Has proton pumps

19. How many carbon atoms are present in a single citrate molecule?

    • 4
    • 5
    • 2
    • 6

20. What key compound produced by the link reaction enters the Krebs cycle?

    • Oxaloacetate
    • Acetyl CoA
    • Pyruvate
    • Citrate

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