Amino acid basic imformation, Cheat Sheet of Biology

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Amino acid

Definition

• Amino acids are organic compounds

containing the basic amino groups (-NH2) and

carboxyl groups (-COOH).

• There are 20 main amino acids which is

found in human body, however there are also

non- proteinogenic amino acids

Fundamental structure

C

H

Nh C

R

O

O

H

• For the 19 amino acids which are chiral, there

exist D and L enantiomers which are

structurally identical molecules that have

opposite absolute configurations around the

chiral carbon.

• As an evolutionary quirk, the human body only

uses L-amino acids to synthesize proteins.

L- amino acid D - amino acid

Amino acids as dipolar ions

• The amino group of an amino acid is a base which is

typically protonated in the environment of the cell

(which has a pH of 7.4) => positive charge.

• The carboxylic acid functional group of an amino

acid is an acid which is typically deprotonated in the

aqueous environment of the cell => negative

charge.

• Since both are ionized, they are by convention

depicted as - NH3* and - COO-.

• Because the uncharged (non-acidic/basic), amino

acids are zwitterions (ions whose charges cancel

out, producing a molecule with net neutral charge).

If an R group

contains an acid,

base, amine, or

alcohol, it will

be hydrophilic.

Any R groups

that do not

contain these

groups will be

considered

hydrophobic