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 usually acts fastest?

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

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

    • It obeys the loudest single voice
    • 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. Why are phosphatases as important as kinases?

    • It removes phosphates, reversing exactly what the cascade added
    • It adds more phosphates to strengthen the signal
    • It builds new receptors for the next signal

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

    • Either input alone would suffice
    • Two weak inputs arriving together cross a threshold neither reaches solo
    • The stronger input blocks the weaker one

  6. What does negative feedback do in a signaling pathway?

    • It amplifies the input without limit
    • It delays the response by one hour
    • It caps the response and keeps the pathway in working range

  7. What is cross-talk between pathways?

    • It blends the two messages before it acts
    • It deletes one pathway entirely
    • It fires both responses at full strength

  8. Predict what a cell does when termination fails.

    • More of the same signal, only louder
    • A stuck switch: action on old news, like endless division
    • An instant return to the resting state
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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 · Attacking the signal at the top shuts everything downstream down fastest.
  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. It removes phosphates, reversing exactly what the cascade added · Without phosphatases every signal would linger.
  5. Two weak inputs arriving together cross a threshold neither reaches solo · Targets demand coincidence, so the cell decides by committee instead of obeying one voice.
  6. It caps the response and keeps the pathway in working range · Output looping back to block an early step throttles the pathway.
  7. It blends the two messages before it acts · One pathway changes how another reads its input through a shared kinase or messenger.
  8. A stuck switch: action on old news, like endless division · When any brake fails, the cell keeps responding as if the signal were still there.
Worksheet · LightMySky