Factors that tend to increase membrane fluidity include:
- A greater proportion of unsaturated fatty acids in the membrane phospholipids. The double bonds in unsaturated fatty acids create kinks that prevent tight packing of lipids, increasing fluidity.
- Shorter fatty acid chains in phospholipids, which are less viscous and more affected by kinetic energy changes, enhancing fluidity.
- Higher temperatures , which provide phospholipids with kinetic energy to move more freely, increasing membrane fluidity.
- Cholesterol acts as a bidirectional regulator. At low temperatures, cholesterol prevents phospholipids from clustering, increasing fluidity. However, at high temperatures, cholesterol stabilizes the membrane and reduces excessive fluidity.
Factors that do not increase fluidity or decrease it include higher proportions of saturated fatty acids, lowering the temperature, and relatively high protein content in the membrane.
In summary, to increase membrane fluidity, the main factors are a greater proportion of unsaturated fatty acids, shorter fatty acid chains, and higher temperature. Cholesterol can increase fluidity at low temperature but generally acts to stabilize membrane fluidity.
