Cells can signal without touching
- The idea
- Predict
- See it
- Why
- Check
The idea
“Cells have to touch, or be wired together, to affect each other.”
It's easy to picture cells bumping into each other or linked by nerves. Often the message is just a molecule drifting between them.
The short version
The mistake: Cells have to touch, or be wired together, to affect each other.
What's actually true: Many signals are molecules released into fluid or blood. A cell with a matching receptor can respond without touching the sender.
- A signaling cell releases a ligand, a molecule that binds a receptor. It travels through the fluid between cells or through the blood.
- Only cells with a receptor that binds that ligand respond. Others ignore it, even right next door.
- Paracrine signals reach nearby cells through the fluid. Endocrine signals are hormones that travel in the blood to distant cells.
- Some signaling does use contact, like gap junctions. A response without contact points to a released molecule.
On the exam: If cells respond without touching, look for a molecule one releases and a receptor that binds it.