膜流动性

Membrane fluidity refers to the ability of the lipid bilayer to remain flexible, which depends on its lipid composition and temperature.

For example, one of the major components, phospholipids, can contain either saturated fatty acid chains, which have the maximum number of hydrogen atoms and no double bonds, or unsaturated fatty acid chains, which have at least one double bond.

When the temperature drops, saturated phospholipids, with their long, straight, fatty acid chains, can pull closer together than the unsaturated ones, which have a kink in their chains due to the double bonds. This extra space preserves some of the membrane fluidity.

Another component, cholesterol, inserts between phospholipids and disrupts the tight packing of fatty acid chains, helping maintain membrane fluidity during colder temperatures.

At higher temperatures, cholesterol restricts phospholipid movement, preventing excessive fluidity in the membrane.

That’s why regulating membrane fluidity is an important cellular response to changes in temperature, such as when seasonal changes cause modifications in the fatty acid composition of fish.