Written by the Fiveable Content Team • Last updated September 2025
Verified for the 2026 exam
Verified for the 2026 exam•Written by the Fiveable Content Team • Last updated September 2025
Definition
A ligand is a molecule that binds to another (usually larger) molecule. In cell communication, it's often the signal molecule that binds to a receptor.
Related terms
Agonist: A substance which initiates a physiological response when combined with a receptor.
Antagonist: A substance that interferes with or inhibits the physiological action of another by competing for its receptor sites.
Hormone: Chemical messengers produced by glands in multicellular organisms that are transported by the circulatory system to target distant organs to regulate physiology and behavior.