Recognize true statements of cholesterol and its fluidity.
1. Cholesterol reduces membrane fluidity in areas called rafts, which hold large amounts of the cholesterol and sphingolipids.
2. Cholesterol restrains crystallization which would otherwise take place in membranes rich in unsaturated fatty acids.
3. Cholesterol is basically buried in bilayer, with its planar rings oriented toward solvent and its hydroxyl group aligned with fatty acid tails of bilayer.
4. Cholesterol raises membrane fluidity which otherwise contains mostly long chain saturated fatty acids.