Amino acids&ProteinsAmino acids&Proteins

These are the building block of protein.They are joined to each other by a specific type of covalent bond called Peptide linkage.

StructureStructure

Amino acids have two characteristic Amino acids have two characteristic functional groups:functional groups:

1)Amino group1)Amino group 2)Carboxyl group2)Carboxyl group 3)Side chain (R)3)Side chain (R) All these are attached to the alpha carbonAll these are attached to the alpha carbon Proline is an exception it has an imino in Proline is an exception it has an imino in

place of amino group.place of amino group.

CharacteristicsCharacteristics

They are soluble in waterThey are soluble in water Insoluble in fat solventInsoluble in fat solvent They have one asymmetric center at alpha They have one asymmetric center at alpha

carbon.carbon. Hence exist in 2 forms:Hence exist in 2 forms: D—formD—form L---formL---form

How ever in proteins they exists in L How ever in proteins they exists in L configuration.configuration.

D—configuration is found in :D—configuration is found in :

antibioticsantibiotics

bacterial cell wall.bacterial cell wall.

At physiologic ph= 7.4 At physiologic ph= 7.4 carboxyl group is dissociatedcarboxyl group is dissociated Forming the negatively charged Forming the negatively charged

carboxylated ion.(-COO-)carboxylated ion.(-COO-) Amino group is protonated (NH3+).Amino group is protonated (NH3+).On the basis of the side chain the amino On the basis of the side chain the amino

acids can be classified.acids can be classified.