Cholesterol affects membrane fluidity by acting as a regulator that maintains an optimal fluid state of the cell membrane. It inserts itself between phospholipid molecules, interacting with their fatty acid chains and modulating their movement. Specifically:
- Cholesterol decreases membrane fluidity in regions rich in unsaturated fatty acids by filling gaps and reducing their movement, making the membrane more rigid.
- Conversely, in regions rich in saturated fatty acids, which pack tightly, cholesterol disrupts this tight packing and increases fluidity.
- Overall, cholesterol makes the membrane less fluid at high temperatures by stabilizing phospholipids and preventing them from moving too freely. At low temperatures, it prevents the membrane from becoming too rigid by interrupting the close packing of phospholipids.
- Cholesterol also contributes to membrane stability by reducing permeability and enhancing the membrane's structural integrity.
Thus, cholesterol serves a dual role in regulating membrane fluidity by buffering temperature effects and maintaining membrane stability and selective permeability.
