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A lipid is a variety of biological molecules that are water insoluble. They are energy-storage molecules and chemical messengers that embrace fats, waxes, oils, hormones, and few membrane elements.Cell membrane contains a number of crucial lipids.

Lipids, unlike other macromolecules, are not water-soluble and do not form lengthy sequences of comparable or repeating smaller units. Triglycerides are fat molecules made up of three fatty acids connected to glycerol.

Lipids differ from nucleic acids, carbohydrates, and proteins as they largely consist of hydrogen, carbon, and oxygen (except for phospholipids which also contain phosphorous). Lipids have a higher energy density per gram than carbohydrates, yet carbohydrates are easier to digest and release energy from than lipids.