Cell Signalling and Receptor Mechanisms · USMLE Step 1

Which scenario best illustrates signal amplification in cell signaling?

  1. One ligand binds one receptor and opens a single ion channel briefly
  2. One ligand–receptor event generates many second messengers that activate many effectors
  3. One receptor permanently binds its ligand, locking the signal on
  4. Each receptor reliably triggers only a single downstream molecule
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Correct answer: One ligand–receptor event generates many second messengers that activate many effectors

Signal amplification occurs when a single ligand–receptor interaction triggers generation of many second messengers or activates many downstream proteins, magnifying the initial signal.

Difficulty: Medium Question 19 of 22

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