Glycolysis and the Link Reaction · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.
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Splitting sugar for quick energy

Science · Organisms & Life Processes · ages 16-18
Name ______________________   Date ____________

  1. What is the net yield of glycolysis per glucose?

    • 4 ATP plus 4 reduced NAD
    • 2 ATP plus 2 reduced NAD
    • No ATP at all

  2. Where does glycolysis happen?

    • In the mitochondrial matrix
    • In the nucleus
    • In the cytoplasm

  3. Glycolysis needs oxygen to run.

    Circle one:   True   False

  4. What is removed from pyruvate in the link reaction, and where?

    • Water, in the cytoplasm
    • Carbon dioxide, in the mitochondrial matrix
    • Oxygen, in the nucleus

  5. Why does glycolysis spend two ATP before it makes any?

    • To prime glucose so it can split evenly
    • To push glucose into the mitochondria first
    • To use up spare energy left from earlier

  6. Per glucose, how many times does the link reaction run, and what does it give?

    • Twice, giving two acetyl CoA, two carbon dioxide and two reduced NAD
    • Once, giving one ATP
    • Four times, giving four ATP

  7. A student says each glucose nets four ATP from glycolysis. What is wrong?

    • Nothing, four is the net gain
    • The payoff phase makes no ATP
    • The net is two

  8. A muscle cell runs short of oxygen. Why does glycolysis keep going?

    • It moves into the mitochondria
    • Fermentation recycles NAD
    • It stops needing glucose
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Answer key

For grown-ups. Fold this page away before handing over the rest.

Splitting sugar for quick energy W1-mt_crbadbBvqB-s1

  1. 2 ATP plus 2 reduced NAD · Four made minus two spent leaves two, plus two reduced NAD.
  2. In the cytoplasm · It runs in the cytoplasm, so no mitochondria are needed.
  3. False · It runs in the cytoplasm with no oxygen involved.
  4. Carbon dioxide, in the mitochondrial matrix · In the matrix, pyruvate loses carbon dioxide and becomes acetyl CoA.
  5. To prime glucose so it can split evenly · The two ATP add phosphate groups that let glucose split evenly into two three-carbon pieces. Those pieces then pay back four ATP.
  6. Twice, giving two acetyl CoA, two carbon dioxide and two reduced NAD · Two pyruvates mean two passes through the link step. Each pass gives one acetyl CoA, one carbon dioxide and one reduced NAD.
  7. The net is two · Gross payoff is four, but the entry fee leaves two.
  8. Fermentation recycles NAD · Recycled NAD keeps the cytoplasmic pathway spinning.
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