Bio Chemistry

BIOCHEMISTRY 3(2+1)

Lesson 10 : Proteins – Synthesis, Structure of Amino Acids, Sources, Functions

Structure of amino acids

There are 20 common amino acids called ?-amino acids because they all have an amino (NH3+) group ( Basic ) and a carboxyl group (COOH) attached to C-2 carbon (a carbon) ( acidic ).

At pH of 7, amino group is protonated (-NH3+) and carboxyl group is ionized (COO-). The amino acid is called a zwitterion.

If pH > pI, amino acid would be negatively charged.

If pH < pI, amino acid would be positively charged.

If pH = pI, amino acid would have no charge.

The carbon is chiral or asymmetric (4 different groups are attached to the carbon; exception is glycine.)

Amino acids exist as stereoisomers (same molecular formula, but differ in arrangement of groups).

Designated D(right) or L(left).

Amino acids used in nature are of L configuration.