Cell signalling = transfer of information from environment → across membrane → into cell

Ensures correct timing, coordination, and specificity of cellular activities

3 stages:

1. Ligand-receptor interaction (reception)

2. Signal transduction

3. Cellular response

Responses include:

• Enzyme activity

• Gene expression

• Cytoskeleton rearrangement

The signal ligand molecule is complementary in shape to a specific site on the receptor.

Types of ligands:

• Hydrophilic/large

  • Cannot cross membrane → bind cell surface receptors

• Hydrophobic/small

  • Diffuse through membrane → bind intracellular receptors