This document classifies and categorizes amino acids in several ways: 1. Chemically, amino acids are classified as monobasic/neutral, basic, or acidic depending on their number of COOH and NH2 groups. Neutral amino acids are further broken down into non-polar, sulfur-containing, hydroxyl, heterocyclic, and aromatic. 2. Amino acids are also classified based on the polarity of their side chains as non-polar, polar with no charge, positively charged, or negatively charged. 3. Nutritionally, amino acids are essential/indispensable, semi-essential, or non-essential based on whether the human body can synthesize them.

1. Classification Of
Amino Acids

2. Amino Acids
 Amino Acids are the building units of proteins linked
together by “Peptide bond”.
 There are about 300 amino acids occur in nature. Only 20 of
them occur in proteins.

3. LEARNING OBJECTIVES
1☺ Chemical classification:
2☺ Classification on the basis of polarity of
the side chain(R):
3☺ Nutritional classification:
4☺ Metabolic classification:

4. 1- Chemical classification:
Standard amino acids
According to number of COOH and NH2 groups i.e. according to net
charge on amino acid.
A- Monobasic, monocarboxylic amino acids i.e. neutral or
uncharged:
The largest group of amino acids

5. Subclassification of neutral amino acids:
1- non-polar aliphatic amino acids
e.g. glycine, alanine, valine, leucine, isoleucine.
2- Sulfur containing amino acids:
e.g. Cysteine and Methionine.
3- Hydroxy amino acids:
e.g. Serine and Threonine.
4- Heterocyclic amino acids:
e.g. Tryptophan & Histidine.
5- Imino acid:
Proline & Hydroxy proline.

6.  6- Aromatic amino acids:
e.g. Phenyl alanine, Tryptophan & Tyrosine

7. B- Basic amino acids: having less COOH group & more
amino groups.
e.g.
a- Lysine.
b- Arginine.
c- Histidine.
C- Acidic Amino acids: having more COOH groups & less
amino group.
e.g.
a- Glutamic acid.
b- Aspartic acid.

8. Non-standard amino acids:
Have similar structure like that of amino
acids but don’t take part in the synthesis of
Proteins(because genes don’t have codons
for them). E.g. Taurine, Ornithine,
Citrulline & GABA(γ-aminobutyric acid)
etc…

9. 2 Classification according to polarity of side chain
(R):
A. Non- polar Amino acids
e.g. Alanine, Leucine, Isoleucine, Valine, Methionine, Phenyl Alanine,
Tryptophan and Proline
B. Polar Amino acids with no charge on “R” group
e.g. Glycine, Serine, Threonine, Cysteine, Glutamine, Asparagine and
Tyrosine
C. Polar Amino acids with positive “R” group
e.g. Lysine, Arginine, Histidine
D. Polar Amino acids with negative “R” group
e.g. Aspartic acid and Glutamic acid

10. 3 Nutritional classification:
1- Essential or Indispensable amino acids: Can’t be
synthesized in the body & have to be taken in the diet.
e.g. Valine, Isoleucine, leucine, Lysine, Methionine, Phenyl Alanine,
Threonine and Tryptophan
2- Semiessential amino acids: These are growth promoters.
Not synthesized in adequate amount in the body.
e.g. Arginine and Histidine.
3- Non essential or Dispensable amino acids: Can be
synthesized in the body & may not be the component of diet.
e.g. Glycine, Alanine, Serine, Cysteine, Asparagine, Glutamine,
Tyrosine, and Proline.

11. 4 Metabolic classification:
according to metabolic or degradation products of amino acids they
may be:
a- Ketogenic amino acids: which give ketone bodies . Lysine and
Leucine are the only pure ketogenic amino acids.
b- Mixed ketogenic and glucogenic amino acids: which give
both ketonbodies and glucose. These are: isoleucine, phenyl alanine,
tyrosine and tryptophan.
c- Glucogenic amino acids: which give glucose. These are:
Glycine, Serine, Valine, Histidine, Arginine, Cysteine, Proline,
Alanine, Glutamine, Asparagine & Methionine.

12. Nutrition & Metabolic AAs
• Non essential as well as
glucogenic AAs: e.g.
Alanine,Arginine, Asparagine,
Asparate, Cysteine, Glutamate,
Glutamine, Glycine, Proline, Serine.
• Non essential & glucogenic
ketogenic AAs: e.g. Tyrosine.

13. • Essential glucogenic AAs: e.g. Histidine,
Methionine, Threonine, Valine.
• Essential glucogenic & ketogenic AAs:
e.g. Isoleucine, Phenyl alanine, Tryptophan.
• Essential ketogenic AAs: e.g. Leucine &
Lysine

14. FARHAN ALI
Roll no. 81
5th
Batch
Session 2013-2017