Q.Give a detailed account of the different types of lipids -- fatty acids, triglycerides, phospholipids and steroids -- describing the structure and principal biological role of each.
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Start your 14-day free trial to unlock the full solution →Lipids are a chemically diverse group united by their insolubility in water and solubility in organic solvents, and are generally built from fatty acids joined to an alcohol. A fatty acid is a long hydrocarbon chain ending in a carboxyl group, classified as saturated when every carbon-carbon bond is a single bond (e.g. palmitic acid, stearic acid -- solid at room temperature, packing tightly) or unsaturated when the chain contains one or more carbon-carbon double bonds (e.g. oleic acid, linoleic acid -- liquid at room temperature, prevented from tight packing by the kinks the double bonds introduce).
Simple lipids, chiefly triglycerides (neutral fats), form when one glycerol molecule is esterified with three fatty acid molecules through three ester bonds, releasing three water molecules; triglycerides are the body's principal energy-storage lipid, held mainly in adipose tissue, yielding more energy per gram than carbohydrate or protein. Compound lipids, chiefly phospholipids, are built on a glycerol backbone esterified with only two fatty acid chains, with the third position instead carrying a phosphate group linked to a polar head group; this gives the molecule an amphipathic character -- a hydrophilic phosphate head and two hydrophobic fatty-acid tails -- which allows phospholipids to self-assemble into the bilayer forming every biological membrane. Glycolipids similarly combine a lipid with an attached carbohydrate group. …
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