132 ^|

A Handbook of Biology

2

COOH

H N

C

H

H



¾

¾



2

3

COOH

H N

C

H

CH



¾

¾



2

2

COOH

H N

C

H

CH OH



¾

¾



Glycine Alanine Serine

(Hydrogen as R group) (Methyl as R group) (Hydroxy methyl as R group)

BÅSËD ØÑ THË ÑÜMBËR ØF ÅMÏÑØ ÅÑD ÇÅRBØXÝL GRØÜPS, THËÝ ÅRË ØF 3 TÝPËS:

Acidic amino acids: e.g. Glutamic acid, Aspartic acid.

Basic amino acids: e.g. Lysine, Arginine

Neutral amino acids: e.g. Valine



Some amino acids are aromatic. E.g. tyrosine, phenylalanine and

tryptophan.



Amino acids have ionizable nature. So, structure of amino acids changes

in solutions of different pH.



Amino acids can behave as zwitter ion (neutral but contains both

positive and negative charges.

3

3

2

(C)

(A)

(B)

R

R

R

NH

CH

COOH

NH

CH

COO

H N

CH

COO

+

+

-

-







¾

¾

¾

¾

¾

¾





B is zwitterionic form

Amino acids can be essential or non-essential.

Essential amino acids:

They

cannot

be

synthesized by the body and should be supplied

through diet. E.g. Lysine, leucine, isoleucine,

tryptophan etc.

(AIPMT 2010)

Non-essential amino acids: They can be

synthesized by the body. E.g. Glycine, alanine,

serine, arginine etc.

AMAZING FACT