Unit 10

Unit - - Proteins and lipids . Structure of proteins About different amino acids may appear in proteins. All amino acids share a common chemical ‘backbone’ and it is these backbones that are linked together to form proteins. Each amino acid also carries a side chain, which varies from one amino acid to another. The side chains make the amino acids differ in sizes, shape and electrical charge. The side chains on amino acids are what makes proteins so varied in comparison with either carbohydrate (or) lipids. Each amino acid contains a carboxyl (COOH) or acidic group and an amino (NH ) or basic group. The amino acids are mostly linked together in forming a protein molecule through NH group of one amino acid condensing with COOH group of another amino acid with the elimination of one molecule of water, and a compound thus formed is called a peptide and the linkage is called ‘ peptide linkage’ . Ø know the effects of protein deficiency in children. Ø gain an understanding of lipids as a concentrated source of energy. Ø differentiate between healthy and unhealthy fats in the diet. . Origin and composition of proteins: Origin Amino acids are small units that combine to form a protein molecule. Plants synthesise amino acids with the help of bacteria and fungi from : (i) soil, which supplies the necessary nitrogen and sulphur; (ii) water, which provides oxygen and hydrogen; and (iii) atmospheric carbon dioxide, which supplies carbon and oxygen. Animals cannot synthesise amino acids from basic elements, but derive them from ingested plants. Thus, the primary source of all proteins is the vegetable kingdom. Composition Proteins are chemical compounds that contain the same atoms as carbohydrate and lipid – Carbon(C), Hydrogen (H) and Oxygen (O). Which is not present in CHO and lipibs. They also contain nitrogen (N) atoms. These Nitrogen atoms give the name ‘amino’ (nitrogen containing) to the amino acids that are the links in the chains referred to as proteins.