Identify true statements of cholesterol and its fluidity.
1. Cholesterol decreases membrane fluidity in areas called rafts, which contain large amounts of sphingolipids and cholesterol.
2. Cholesterol inhibits crystallization that would otherwise occur in membranes rich in unsaturated fatty acids.
3. Cholesterol is generally buried in a bilayer, with its planar rings oriented toward the solvent and its hydroxyl group aligned with the fatty acid tails of the bilayer.
4. Cholesterol increases membrane fluidity that otherwise contains mostly long chain saturated fatty acids.