Function of cholesterol in plasmalemma is to
The fluidity of the lipid bilayer is decreased in following three ways Lowering temperature Increasing saturation of fatty acyl tails in phospholipid membrane Increase membrane cholesterol content. Cholesterol interacts with the phospholipid membrane containing fatty acyl chains, compacting them, constraining the motion in bilayers, hence decreasing the fluidity. Ref: Lehninger 30e pg 395.