Library · Cellular process
How cells send signals to each other
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Cells do not whisper to each other: they send molecules. The one doing the sending releases a ligand, the molecule that carries the message, and that ligand binds a receptor, the matching piece on the cell receiving the message, which is called the target cell. Every signal travels with its own key, and it opens only the lock made for it.
The interesting part starts on the other side. When the ligand latches onto the receptor at the surface, a signaling pathway begins: a chain of steps that happens inside the cell, one after another, until it reaches whatever needs to change.
Signals fall into four categories, and what separates them is how far the message has to travel to reach the target cell. They are called paracrine, endocrine, autocrine, and direct through gap junctions.
And there is one detail that explains why a tiny amount of messenger goes such a long way: the chain amplifies. A single enzyme linked to the receptor can activate many copies of the next component.
In brief
A cell sends its signal by releasing a ligand, the molecule that binds the receptor on the target cell.
Every signal carries its own key, and it opens only the lock made for it.
Binding to the surface receptor starts a signaling pathway, a chain of steps inside the cell.
The four categories of signaling differ by how far the message travels: paracrine, endocrine, autocrine, and direct through gap junctions.
And the pathway amplifies: one receptor-linked enzyme can activate many copies of the next component.
Sources (2)
- OpenStax, Rice UniversitySignaling Molecules and Cellular Receptors, Biology 2ePublished
- OpenStax, Rice UniversityPropagation of the Signal, Biology 2ePublished
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