How do phospholipids with unsaturated hydrocarbon chains affect membrane fluidity?

Phospholipids with unsaturated hydrocarbon chains introduce kinks in their fatty acid tails, preventing them from packing closely together. This increased spacing between the phospholipids enhances membrane fluidity, making the membrane more flexible and permeable. As a result, membranes enriched with unsaturated fatty acids can better adapt to temperature changes and maintain functionality in various conditions.