Cell Signalling and Receptor Mechanisms · USMLE Step 1

What is a common mechanism for terminating signaling from many cell-surface receptors after ligand binding?

  1. Permanent and irreversible inactivation of every cell receptor
  2. Immediate enzymatic destruction of the ligand in the extracellular space
  3. Endocytosis of the ligand–receptor complex, then ligand breakdown or recycling
  4. Phosphorylation of the extracellular domain to block further ligand binding
Show answer and explanation

Correct answer: Endocytosis of the ligand–receptor complex, then ligand breakdown or recycling

Receptor internalization (endocytosis) removes ligand–receptor complexes from the cell surface; ligand is degraded and receptor may be recycled or degraded, terminating the signal.

Difficulty: Medium Question 10 of 22

Practice all 22 Cell Signalling and Receptor Mechanisms questions

Keep practicing

More Cell Signalling and Receptor Mechanisms questions