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 membrane is a thin barrier that separates the inside from the outside or different compartments within an organism. In biology, membranes are often composed of lipid bilayers with embedded proteins.
Related terms
Selective permeability: The property of membranes that allows them to regulate what substances can enter or leave cells.
Phospholipid bilayer: A double layer of phospholipids that makes up most cellular membranes.
Transport proteins: Proteins embedded in the membrane that help facilitate the movement of specific molecules across it.