Transition temperature of lipid bilayers of cell membranes is increased by

The cholesterol content of the membrane alters the fluidity of the membrane. When cholesterol concentration increases, the membrane becomes less fluid on the outer surface, but more fluid in the hydrophobic core. The effect of cholesterol on membrane fluidity is different at different temperatures. At temperature below the Tm, cholesterol increases fluidity and thereby permeability of the membrane. At temperatures above the Tm, cholesterol decreases fluidity.Ref: DM Vasudevan, page no: 11