Amino acids are the building blocks of proteins. Each amino acid contain a centrally located carbon atom called alpha carbon to which four groups are attached: basic amino group, an acidic carboxyl group, a hydrogen atom and a group of varying chemical structures called a side chain group.
Functions of Amino acids1. Building blocks of Proteins: Protein are polymers of amino acids. The specificity of different proteins is due to number and sequence of amino acids present in them.
2. The amino acid glycine form porphyrin nucleus in chlorophyll and heme proteins like haemoglobin and cytochromes.
3. Cysteine: It produces disulphide linkages amongst polypeptides.
4. Tryptophan: The amino acid give rise to plant hormone IAA (Indole Acetic Acid) and nicotinamide.
5. Tyrosine: It forms skin pigment melanin and two hormones thyroxine and adrenaline.
6. Alanine: The amino acid β alanine forms coenzyme A (CoA) and vitamin panthothenic acid.
7. Urea cycle: Two nonprotein amino acids, Ornithine and Citrulline, are involved in urea cycle.
8. Diaminopimelic acid: It occurs in bacterial cell wall. Diaminopimelic acid is an intermediate lysine synthesis.
9. Methionine: It provides methyl group in many reactions.
10. Aspartame: It is synthetic peptide that is some 200 times sweeter than sucrose. Aspartame is without unpleasant after taste of saccharin. It is, however, not suitable to people suffering from phenylketonuria.
11. Enkephalins: They are natural short lived pentapeptide pain killers produced by nerve cells in brain.
12. Biological buffers: Being amphoteric, amino acids functions as buffers.
13. Antibiotics: Several antibiotics possess protein and nonprotein amino acids, e.g., Gramicidin, Tyrocidin, Pencillin.
14. Histamine: It is formed by decarboxylation of amino acid Histidine. All types of cells can do it. Histamine is formed during allergic inflammatory reactions. It causes dilation of capillaries, decreases blood pressure, constricts smooth muscles (e.g., bronchi, uterus) and increases gastric secretions.
15. Glutathione: It is coenzyme of oxidation reduction reactions which consists of a tripeptide of Glutamic acid, Cysteine and Glycine. The chemical is important in preventing oxidative damage erythrocytes.
16. Peptide Hormones: A number of hormones are peptide in nature. Oxytocin and Vassopressin are nonpeptides of posterior pituitary. Angiotensin is also a peptide.
17. Gluconeogenesis: Excess amino acids are deaminated and their organic acids are converted to glucose and other carbohydrates.
18. Peptidoglycans: They bear small peptides having both protein amino acids and non protein amino acids. Peptidoglycans are structural unit of prokaryotic cell wall.
19. Bradykinin: It is a nonapeptide origin which is pain stimulant in region of tidsue damage, powerful arterior dialatator and brings about increases capillary permeability.