Classification & qualitative tests of amino acids Classification based on nutrition, structure and polarity Color reaction of amino acids, ninhydrin test, millions test, sakaguchi test, lead acetate test

1. BIOCHEMISTRY & CLINICAL
PATHOLOGY
TOPIC- CLASSIFICATION & QUALITATIVE TESTS OF
AMINO ACIDS
PRESENTED BY-
SHWETA MISHRA

2. CLASSIFICATION OF AMINO ACIDS
BASED ON
NUTRITION

3. A. BASED ON POLARITY:
E.G. Alanine E.G. Lysine E.G. Aspartic acid
Leucine Arginine Glutamic acid
Isoleucine Histidine
Valine
Proline
NON-POLAR
AMINO ACIDS
POLAR AMINO
ACIDS
WITH POSITIVE ‘R’
GROUP
POLAR AMINO
ACIDS
WITH NEGATIVE ‘R’
GROUP

4. B. BASED ON NUTRITION
1. Essential ‘OR’ indispensible amino acids-
● The amino acids that cannot be synthesized by the human body are essential amino acids.
● Must be obtain through diet.
● Example-[AVHILLMPTT] Arginine, Valine, Histidine, Isoleucine, Leucine, Lysine,
Methionine, Phenylalanine, Threonine, Tryptophan.
1. Non-essential ‘OR’ dispensible amino acids-
● The amino acids that can be synthesized by the human body are essential amino acids.
● Not necessary to obtain from diet.
● Example- Glycine, Alanine, Serine, Glutamate, Glutamine, Tyrosine, Proline.

5. C. BASED ON THE STRUCTURE
1. AMINO ACIDS WITH ALIPHATIC SIDE CHAINS-
Name Symbol Structure
Glycine Gly R=H
Alanine Ala R=CH3
Valine Val R=
Leucine Leu R=

6. 2. AMINO ACIDS CONTAINING (-OH) GROUPS-
Name Symbol Structure
Serine Ser R=
Threonine Thr R=

7. 3. SULFUR CONTAINING AMINO ACIDS-
Name Symbol Structure
Cystein Cys R=
Methionine Meth R=

8. 4. AROMATIC AMINO ACIDS-
Name Symbol Structure
Phenylalanine Phe R=
Tyrosine Tyr R=

11. QUALITATIVE TESTS OF AMINO ACIDS
1. NINHYDRIN TEST-
All amino acids with free alpha-amino groups will react with Ninhydrin to give deep Blue-
Purple color.(General test for all amino acids).
1. MILLON’S TEST-
This is a specific test for the amino acid Tyrosine. It gives White precipitate with Millon’s
reagent.
1. SAKAGUCHI TEST-
This is a specific test for the amino acid Arginine. It gives a Red color with Sakaguchi reagent.

12. 4. LEAD-ACETATE TEST OR LEAD-SULFIDE TEST-
It is a specific test for sulfur containing amino acids. On boiling with strong alkali, the amino
acid splits out sulfur which combines with lead acetate [Pb(CH3COO)2] forming a Black
precipitate of lead sulfide(PbS).

13. THANK YOU