Co-transport and Coupled Movement Across Membranes · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

How gut cells pull in glucose

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

  1. What makes a carrier a symporter?

    • It couples movement in the same direction
    • It couples movement in opposite directions
    • It carries one substance without a coupled partner

  2. Which protein uses ATP directly during sodium-dependent glucose entry into a gut lining cell?

    • The sodium glucose symporter during coupled entry
    • The sodium potassium pump during sodium export
    • A glucose carrier during downhill glucose movement

  3. Which substance moves down its electrochemical gradient through the gut sodium glucose symporter?

    • Potassium ions
    • Glucose molecules
    • Sodium ions

  4. A cell starts without a sodium gradient. Which sequence lets the pump support glucose entry against its concentration gradient?

    • Symporter uses ATP; glucose entry then powers sodium export
    • Glucose enters alone; its entry then builds the sodium gradient
    • Pump uses ATP; its gradient then supports coupled entry

  5. The sodium potassium pump is blocked. As the sodium gradient weakens, what happens to sodium-dependent glucose entry?

    • It decreases as the gradient supplies less energy
    • It increases as the symporter starts using saved ATP
    • It stays unchanged because the gradient has no role

  6. An antiporter couples entry of substance X to movement of substance Y across the same membrane. Which movement of Y accompanies X entering?

    • Y enters the cell through the same carrier
    • Y stays outside without crossing the membrane
    • Y leaves the cell through the same carrier

  7. Blocking the sodium potassium pump must stop sodium-dependent glucose entry immediately, even if a driving sodium gradient remains.

    Circle one:   True   False

  8. A student calls sodium-dependent glucose entry primary active transport because it depends on ATP. Which correction explains why it is secondary?

    • It moves glucose without any energy input, so the uptake is passive diffusion
    • It moves glucose through the sodium potassium pump, which splits ATP directly
    • It uses energy from an ion gradient maintained by the ATP-driven pump
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Answer key

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

How gut cells pull in glucose W1-mt_pzQ8n3FWNV-s1

  1. It couples movement in the same direction · Symport means coupled movement in the same direction. The sodium glucose symporter brings both substances into the cell.
  2. The sodium potassium pump during sodium export · The sodium potassium pump uses ATP directly. The symporter uses energy from the sodium gradient maintained by that pump.
  3. Sodium ions · Sodium enters down its electrochemical gradient. Its movement supplies energy for coupled glucose entry against glucose's concentration gradient.
  4. Pump uses ATP; its gradient then supports coupled entry · The pump must establish a sodium gradient before that gradient can provide energy for coupled glucose entry.
  5. It decreases as the gradient supplies less energy · A weaker sodium gradient supplies less energy for coupled glucose entry. The symporter does not switch to using ATP directly.
  6. Y leaves the cell through the same carrier · An antiporter couples movement in opposite directions. Since X enters, its coupled partner Y leaves the cell.
  7. False · The symporter may use an existing driving gradient briefly after the pump is blocked. Uptake decreases as that gradient weakens.
  8. It uses energy from an ion gradient maintained by the ATP-driven pump · The symporter depends indirectly on ATP. It uses energy from sodium moving down a pump-maintained gradient, making glucose uptake secondary active transport.
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