Membrane Fluidity: Cold-water fish adjust their membrane composition to stay functional in freezing temperatures.
Saturated Fatty Acid
Straight chains pack tightly
Unsaturated Fatty Acid
Kinks prevent tight packing
Double bonds in unsaturated fatty acids create kinks in the carbon chain
Kinks prevent tight packing, keeping membranes fluid at low temperatures
Fish increase unsaturated fatty acids in winter through dietary changes
Cholesterol as a Fluidity Buffer: Cholesterol molecules wedge between phospholipids, preventing tight packing at low temps (increasing fluidity) while restricting movement at high temps (decreasing fluidity). This keeps membrane fluidity stable across temperature changes.
Use the temperature slider to observe how membrane fluidity changes!