Unit 3 - Macromolecules: Lipids & NucleicAcids Macromolecules: Lipids • Lipids - large molecules (not truly polymers) that don’t mix well with water. • Most heterogenous class of molecules. • Major component of cell membranes. • 3 major classes of lipids: fats, phospholipids, steroids Lipids: Fats • Fat - made from glycerol and fatty acids. Hydrophobic due to the non polar C and H bonds in the hydrocarbon chain, water molecules don’t bond with fat. • Glycerol: an alcohol with 3 carbons with a hydroxyl group each. • Fatty acids: made of a long carbon skeleton with a carboxyl group at one end with the rest being a hydrocarbon chain. • To make a fat, 3 fatty acid molecules (can be same or different) are joined to glycerol through ester linkage, creating triacylglycerol, which is non polar. • Functions: • Energy storage. • 1 gram of fat is twice as much energy as 1 gram of a polysaccharide like starch. Saturated v.s unsaturated fat • Saturated or unsaturated refers to the fatty acid’s hydrocarbon chain structure. • Saturated fat - saturated with hydrogen, no double bonds between carbon atoms to allow maximum flexibility of the molecule. • Most animal fats are saturated (e.g lard, butter) • The lack of double bonds allow the molecules to pack together. • Usually solid at room temperature. • Unsaturated fat - has double bonds with less hydrogen, often creating a “bend” or kink in the hydrocarbon chain. • Fats of plants, fish. • Referred to as oils (e.g olive oil