- Fluidity of membrane is highly dependent upon the lipid composition of the membrane.
- Cholesterol modifies the fluidity of the membrane.
At temperature below Tm it interferes with the interaction of the hydrocarbon tails of fatty acid and thus increasing fluidity.
At temperature above Tm it limits fluidity i.e. decreases fluidity.
- As membrane fluidity increases so its permeability to water and other small hydrophilic molecules.
- Membrane lipids are amphipathic and form bilayer.
- Fluidity is increased by — high temperature, more no. of double bonds, low Tm e.g. Unsaturated Fatty acid.
- Fluidity is decreased by — Saturated fatty acid (high Tm)
E.g. Stearic acid Palmitic acid.