The cell decides what a signal does
- The idea
- Predict
- See it
- Why
- Check
The idea
“A signal carries its own instructions, so every cell it reaches does the same thing.”
Hormones are usually taught by one job, like epinephrine raising blood sugar. So it's easy to picture the hormone carrying that job everywhere.
The short version
The mistake: A signal carries its own instructions, so every cell it reaches does the same thing.
What's actually true: One signal can cause different responses, because each cell's own relay and target proteins decide what happens.
- A signal molecule only changes the shape of the receptor it binds. It carries no instructions.
- The receptor sets off a relay, a chain of molecules inside the cell. Relay proteins like PKA act on whatever targets that cell has.
- Different cell types express different genes, so they make different targets.
On the exam: A signal only changes its receptor. The cell's own relay and target proteins decide the response.