Biology / Unit 4 Bio 0801 short lesson, about 20 seconds
Second Messengers, Defined
Captions available
The idea
A second messenger is a small molecule that spreads a signal through the cytoplasm after the first messenger, the ligand, has bound its receptor at the membrane.
In practice
A single receptor activation can trigger a burst of second messengers that diffuse quickly through the cytoplasm.
Where people slip
A second messenger never touches the ligand — it is generated fresh inside the cell after receptor activation.
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