Signal Integration: Cross-talk, Feedback and Termination · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Cells decide by committee

Science · Organisms & Life Processes · ages 20-21
Name ______________________   Date ____________

  1. Which shutoff step stops fresh input from reaching lower steps?

    • Clearing the active messenger near the top
    • Growing new receptors at the surface instead
    • Copying more target genes

  2. How does a cell handle receiving two signals at once?

    • It obeys only the loudest single voice and ignores the rest
    • It always averages all inputs
    • It reads combinations rather than single inputs

  3. The same hormone divides one cell type and only nudges its neighbor. True or false?

    Circle one:   True   False

  4. Phosphatases add more phosphates to strengthen the signal. True or false?

    Circle one:   True   False

  5. Two pathways converge on one target and fire it, though neither fires it alone. How?

    • Either input alone would already suffice on its own
    • Together they cross a threshold neither reaches solo
    • The stronger input simply blocks the weaker one entirely

  6. Negative feedback amplifies the input without limit. True or false?

    Circle one:   True   False

  7. Cross-talk means each pathway fires at full strength alone. True or false?

    Circle one:   True   False

  8. Predict what a cell does when termination fails.

    • More of the same signal, only louder and longer lasting
    • A stuck switch: action on old news
    • An instant return to the resting state at once
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Answer key

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

Cells decide by committee W1-mt_Io2P-l38Xq-s1

  1. Clearing the active messenger near the top · Top clearance stops fresh input; lower steps still need phosphatases and clearance to quiet.
  2. It reads combinations rather than single inputs · Shared kinases and messengers let one pathway raise or lower the gain of another.
  3. True · Context is carried by which pathways are active together, so identical signals end differently.
  4. False · Phosphatases strip phosphates; without them signals linger.
  5. Together they cross a threshold neither reaches solo · Targets demand coincidence, so the cell decides by committee instead of obeying one voice.
  6. False · Output looping back blocks an early step and caps the response.
  7. False · Shared parts blend messages before action.
  8. A stuck switch: action on old news · When any brake fails, the cell keeps responding as if the signal were still there.
Worksheet · LightMySky