The Krebs Cycle and the Reduced Carriers · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

The Carrier Factory

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

  1. What fuel enters the Krebs cycle?

    • Acetyl CoA, joining oxaloacetate
    • Glucose, joining oxaloacetate
    • Carbon dioxide, joining oxaloacetate

  2. Where does the Krebs cycle run?

    • In the cell cytosol
    • In the mitochondrial matrix
    • Across the inner membrane

  3. How much carbon dioxide leaves in one turn of the cycle?

    • One molecule
    • Six molecules
    • Two molecules

  4. What are reduced NAD and reduced FAD carrying?

    • Carbon dioxide and water
    • Hydrogen and high energy electrons
    • ATP and oxygen

  5. One turn releases 2 carbon dioxide molecules. One glucose sends acetyl through two turns. How many carbon dioxide molecules is that?

    Answer: ______________

  6. Why is the cycle called the main source of carriers rather than of ATP?

    • It burns carriers to release heat
    • It makes most of the ATP directly
    • Many carriers, one ATP

  7. You breathe out carbon dioxide all day. Where did those carbons pass through?

    • Glucose broken down through the Krebs cycle
    • Oxygen breathed in during exercise
    • Water split inside the lungs

  8. A student claims the cycle matters because of its large direct ATP output. 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.

The Carrier Factory W1-mt_eviWcVke2x-s1

  1. Acetyl CoA, joining oxaloacetate · Acetyl CoA from the link reaction joins oxaloacetate to form citrate.
  2. In the mitochondrial matrix · The cycle turns in the matrix, where acetyl CoA arrives from the link reaction.
  3. Two molecules · Two carbons leave as carbon dioxide in each turn.
  4. Hydrogen and high energy electrons · They carry hydrogen and high energy electrons to the electron transport chain.
  5. 4 · Two turns at two molecules each gives four molecules per glucose.
  6. Many carriers, one ATP · One direct ATP per turn is tiny next to what the loaded carriers later earn at the chain.
  7. Glucose broken down through the Krebs cycle · Glucose carbons travel through the link reaction and the cycle before leaving as carbon dioxide.
  8. False · Its direct ATP is tiny. It matters because of the carriers it loads.
Worksheet · LightMySky