4.1 Cell Communication

Cells send and receive signals

Cells coordinate their activities by sending chemical signals. A signal only affects a target cell that has the right receptor to detect it. Signaling ranges from touching neighbors to messaging across the whole body.

Types of signaling

Direct contact: neighboring cells communicate through gap junctions (animals) or plasmodesmata (plants). Local signaling: paracrine signals affect nearby cells; synaptic signals cross a neuron gap. Long-distance: endocrine signaling uses hormones carried in the bloodstream. Bacteria even coordinate through quorum sensing.

Key terms

Cell signaling

How cells communicate using chemical signals detected by target-cell receptors.

Endocrine signaling

Long-distance signaling using hormones carried in the bloodstream.

Paracrine signaling

Local signaling that affects nearby cells.

Receptor

A protein that detects a specific signal molecule on or in the target cell.

Gap junction / plasmodesmata

Channels for direct communication between adjacent cells (animal / plant).

Try an AP-style question

A neurotransmitter released from one neuron travels across a tiny gap to bind receptors on the next neuron. This is an example of…

1. direct contact through gap junctions
2. long-distance endocrine signaling
3. signaling by a hormone in the blood
4. short-distance (synaptic) signaling