Amino acids
Amino acids are the units of proteins. this molecule contains an alpha carbon which is the central carbon, in its four valencies it attaches with an amino group, a carboxyl group, a hydrogen group, and a R group. there are many amino acids but among them, 20 amino acids form all the proteins of living organisms. depending on the R group the amino acids are classified into 5 groups ( in some cases they are classified into 4 groups). These groups are: 1) Nonpolar aliphatic: glycine, alanine, valine, leucine, isoleucine, methionine, proline 2) nonpolar aromatic: tryptophan, phenylalanine, tyrosine. 3) polar uncharged: serine, threonine, asparagine, glutamine, cysteine 4) polar positively charged: arginine, histidine, lysine 5) polar negatively charged: aspartate, glutamate Some facts > Amino acids have two isomeric forms: L-isomer and D-isomer. all living cells contain an L-isomeric form. > All the amino acids that take part in the formation of ribosomal proteins have a S-confi...