A cell can get the signal and still not respond
- The idea
- Predict
- See it
- Why
- Check
The idea
“If the cell didn't respond, the signal was never made or never reached the receptor.”
When nothing happens, it's easy to blame the signal, since it comes first. But a break at any step in a pathway looks the same from outside.
The short version
The mistake: If the cell didn't respond, the signal was never made or never reached the receptor.
What's actually true: No response only means some step failed. Check whether the signal was there and bound before you blame it.
- Signaling has three stages. In reception, the signal binds its receptor. In transduction, relay molecules pass the message on. Then comes the response.
- Look for evidence at each stage. Bound signal shows reception happened. A rise in a second messenger like cAMP shows the relay started inside the cell.
- If cAMP rises and nothing follows, the break is after cAMP. It could be a kinase cAMP activates, that kinase's target or the response protein.
- Blame the signal only when the data show it was missing or never bound. A receptor that binds but can't pass the message on is a break after binding.
On the exam: No response means some link broke. Find the last step with evidence it worked before you blame the signal.