Q.What are 'nucleic acids'? Define complex lipids. Mention any 'two' functions of lipids.

Nucleic acids carry genetic information as nucleotide polymers; complex lipids hydrolyse to extra non-fatty-acid, non-alcohol components; lipids serve mainly as an energy store and as membrane building blocks.

Nucleic acids: biopolymers (polynucleotides) built from repeating nucleotide units (each nucleotide = a nitrogenous base + a pentose sugar + a phosphate group), found as DNA (deoxyribonucleic acid) and RNA (ribonucleic acid) in living cells. They store and transmit hereditary/genetic information and direct protein synthesis.

Complex lipids: lipids which, in addition to fatty acid(s) and an alcohol, contain other groups upon hydrolysis. For example, phospholipids (e.g. lecithin) hydrolyse to give fatty acids, glycerol, phosphoric acid and a nitrogenous base; glycolipids hydrolyse to give fatty acids, an alcohol (often sphingosine) and a carbohydrate (sugar) unit. (This distinguishes them from 'simple lipids' like fats/oils/waxes, which hydrolyse to give only fatty acids and an alcohol.)

Two functions of lipids:

1. Energy storage: fats are the body's most concentrated, long-term energy reserve, yielding roughly twice the energy per gram compared to carbohydrates or proteins on complete oxidation. …