Digestion and Absorption in the Mammalian Gut · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

How your gut moves food into blood

Science · Organisms & Life Processes · ages 16-17
Name ______________________   Date ____________

  1. What does your large intestine take back from leftover material?

    • Acids and chyme
    • Glucose and amino acids
    • Water and salts

  2. Where do most digestion and almost all absorption happen?

    • In the small intestine
    • In the large intestine
    • In the stomach

  3. Villi and microvilli speed absorption by multiplying the gut surface area.

    Circle one:   True   False

  4. Blood in a villus already holds more glucose than the gut fluid. How does more glucose still get in?

    • It waits until the blood empties fully
    • It rides with sodium down the sodium gradient
    • It diffuses backward through the wall

  5. Two guts absorb the same sugar. One has tall dense villi and the other is smooth. Which absorbs faster, and why?

    • The folded one, because crossing rises with surface area
    • The smooth one, because food moves faster
    • Both equal, because area changes nothing

  6. A textbook says villi pump nutrients by themselves. What is wrong with this claim?

    • Villi digest food before absorbing it
    • Villi send nutrients to the stomach
    • Villi are a surface for crossing, not pumps

  7. A mutant carrier binds glucose but ignores sodium. What happens to glucose uptake against its gradient?

    • It fails, because the pull from the sodium gradient is lost
    • It speeds up, because glucose travels alone
    • It moves to the large intestine instead

  8. A drug flattens villi but leaves enzymes intact. Which step of getting energy suffers, and why?

    • Digestion, because enzymes vanish
    • Absorption, because the crossing surface shrinks
    • Elimination, because water stays
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Answer key

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

How your gut moves food into blood W1-mt_xZ2-3ZClDa-s1

  1. Water and salts · The large intestine absorbs water and salts, while its bacteria produce some vitamins.
  2. In the small intestine · Most chemical digestion finishes in the small intestine, and almost all absorption happens across its lining.
  3. True · More membrane means more room for molecules to cross each second.
  4. It rides with sodium down the sodium gradient · A carrier moves glucose with sodium, and the sodium gradient supplies the pull.
  5. The folded one, because crossing rises with surface area · Folding packs a huge surface into a small space, and more area means faster crossing.
  6. Villi are a surface for crossing, not pumps · Villi neither digest food nor pump most nutrients. They are a huge thin surface with blood behind it.
  7. It fails, because the pull from the sodium gradient is lost · Without sodium sliding down its gradient, the carrier cannot drag glucose uphill into blood.
  8. Absorption, because the crossing surface shrinks · Enzymes still break food down, but fewer folds mean less membrane for products to cross.
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