AP Biology / Unit 4: Cell Communication and Cell Cycle
4.2 Introduction to Signal Transduction
Notes
Signaling has three stages:
- Reception: a ligand binds a receptor (on the membrane, or inside the cell for nonpolar ligands like steroids).
- Transduction: the signal is relayed, often through a cascade.
- Response: gene expression, enzyme activity, or other changes.
Practice
Steroid hormones usually bind receptors:
They cross the membrane.
The correct order:
Bind, relay, act.
A ligand is:
It fits the receptor.
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