> Lipids

Lipids tend to be hydrophoibic ( water-fearing ) but carbohydrates and proteins tend to be hydrohibic ( water loving ). Lipids are formed by condensation reactions between fatty acids and an alcohol. Fats ( found in animals ) and oils ( found in plants ) are two types of lipids.

> Fatty acids contain the acidic group -COOH. They have a general formula of RCOOH where R is a hydrocarbon chain: C3 H7 . A common fatty acid has around 14 to 22 carbon atoms in it. Fatty acids that have a double bond are called unsaturated but not all do.

3 fatty acids can bond from the carboxyl group to a glycerol molecule, to from a triglyceride and 3 molecules of water.

> Proteins

Proteins are macromolecules which are composed of polypeptides. They are used for transport, movement, support, structure, communication and disease defence.

1 aminoacid make a monopeptide. 2 aminocaids make a dipeptide. Bonds between aminoacids chains are called peptide bonds form by a condensation reaction. A common protein is called collagen.

> Aminoaciods:

20 aminoacids are common in aur body but there are more than 170. The common structure of an aminocacids is this: