Anaerobic Routes and the ATP Yield Compared · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Running on Fumes

Science · Organisms & Life Processes · ages 17-18
Name ______________________   Date ____________

  1. How much ATP does the anaerobic route net per glucose?

    • Only 2 ATP
    • About 20 ATP
    • About 38 ATP

  2. About how much ATP does one glucose yield with oxygen?

    • 2 ATP
    • 36 to 38 ATP
    • Over 100 ATP

  3. What does a muscle cell make from pyruvate when oxygen runs low?

    • Ethanol and carbon dioxide
    • Lactate
    • Glucose again

  4. Why does a cell without oxygen turn pyruvate into lactate?

    • To free NAD+ so glycolysis can continue
    • To make extra ATP beyond glycolysis
    • To store oxygen for later use

  5. What does a yeast cell make from pyruvate without oxygen?

    • Lactate only
    • Oxygen and water
    • Ethanol and carbon dioxide

  6. One glucose nets 2 ATP without oxygen. A cell breaks down 3 glucose molecules this way. What is the total net ATP?

    Answer: ______________

  7. A sprinting muscle accepts lactate and tiny ATP instead of stopping. Why is that worth it?

    • It keeps NAD+ flowing so glycolysis survives
    • It stores spare ATP for the next sprint
    • It avoids using any glucose at all

  8. Fermentation exists to make extra ATP on top of what glycolysis gives. This claim is true.

    Circle one:   True   False

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Answer key

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

Running on Fumes W1-mt_LBZ4laMfqb-s1

  1. Only 2 ATP · Without the chain only glycolysis pays, so the net stays at 2 ATP.
  2. 36 to 38 ATP · The full chain to oxygen pays about 36 to 38 ATP per glucose.
  3. Lactate · Muscle cells reduce pyruvate to lactate to free NAD+ during hard work.
  4. To free NAD+ so glycolysis can continue · The lactate step exists to regenerate NAD+, not to make extra ATP.
  5. Ethanol and carbon dioxide · Yeast ferments pyruvate to ethanol plus carbon dioxide, which raises bread and fizzes beer.
  6. 6 · Three glucose at 2 ATP each gives 6 ATP in total.
  7. It keeps NAD+ flowing so glycolysis survives · Keeping glycolysis alive matters more than the lost yield, and only freed NAD+ does that.
  8. False · Fermentation makes no extra ATP. It only frees NAD+ to protect glycolysis.
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