The Pentose Phosphate Pathway and Reducing Power for Biosynthesis · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

The side loop that builds and shields

Science · Biochemistry & Molecular Biology · ages 21-22
Name ______________________   Date ____________

  1. What does the oxidative branch produce?

    • ATP directly
    • NADPH
    • Oxygen gas

  2. Where does the pentose phosphate pathway branch off?

    • At glucose 6 phosphate
    • At pyruvate
    • At acetyl CoA

  3. NADPH powers biosynthesis and antioxidant defence, while NADH feeds energy burning.

    Circle one:   True   False

  4. A rapidly dividing cell runs both branches hard. Why both?

    • It needs ribose for genomes and NADPH for membranes and cover
    • It needs to stop glycolysis entirely
    • It needs to destroy its own nucleotides

  5. Why does the cell keep two different reduced carriers instead of one?

    • Because carriers evaporate quickly
    • Because one carrier cannot dissolve in water
    • So burning and building can be tuned separately

  6. What happens to the leftover carbons from the nonoxidative branch?

    • They leave the cell as waste
    • They return to glycolysis through shared intermediates
    • They turn directly into proteins

  7. A cell short of ribose but rich in NADPH should run the nonoxidative branch to reshuffle sugars.

    Circle one:   True   False

  8. A patient with gatekeeper deficiency suffers red cell breakage under oxidative stress. Why red cells first?

    • Red cells contain no glucose at all
    • Red cells never face oxidative stress otherwise
    • Red cells lack mitochondria, so the loop is their only NADPH source
LightMySky · lightmysky.comW1-mt_2p-JnaEaTO-s1

Answer key

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

The side loop that builds and shields W1-mt_2p-JnaEaTO-s1

  1. NADPH · Oxidising glucose 6 phosphate reduces NADP to NADPH as the byproduct.
  2. At glucose 6 phosphate · Glucose 6 phosphate sits at the fork between glycolysis, storage, and the side loop.
  3. True · The cell splits carriers by job: one builds and shields, the other burns.
  4. It needs ribose for genomes and NADPH for membranes and cover · Division demands raw material twice over: sugar backbones and reducing power.
  5. So burning and building can be tuned separately · Separate pools let the cell raise defence without revving energy burning, and back.
  6. They return to glycolysis through shared intermediates · The loop design rejoins the main road, so flux serves building without wasting carbon.
  7. True · The two branches tune independently, so the cell can make sugar without extra reducing power.
  8. Red cells lack mitochondria, so the loop is their only NADPH source · Other cells fall back on mitochondrial sources, but red cells have no such backup.
Worksheet · LightMySky