The fluid-mosaic model and movement across membranes: diffusion, facilitated diffusion, osmosis, active transport, endocytosis and exocytosis.
The cell-surface membrane controls what enters and leaves the cell. Its structure is described by the fluid-mosaic model.
The fluid-mosaic model
A phospholipid bilayer with hydrophilic heads facing the watery solutions and hydrophobic tails inside. It is "fluid" (phospholipids move) and a "mosaic" of proteins:
- Channel proteins — water-filled pores for specific ions/molecules (facilitated diffusion).
- Carrier proteins — change shape to move substances (facilitated diffusion and active transport).
- Cholesterol — sits between phospholipids, regulating fluidity and stability.
- Glycoproteins/glycolipids — cell recognition and receptors.
Viewing only
This content is free to read on superexams.com and cannot be printed or downloaded.
Read the full note — free
Create a free account to read this note in full. Every free account gets 2 complete revision notes — no card needed.