1. AMINO
ACID

2. DEFINATION
A protein molecule consists of one or more long unbranched polymer chains composed of numerous small subunits or monomers is called amino acids .
There are 20 amino acids from which 18 have same structure.

3. STRUCTURE
Amino acids have a central chiral carbon atom called alpha carbon. Groups attached to carbon atom are:
A hydrogen atom (-H-)
An amino group (-NH2)
A carboxyl group (-COOH)
A carbon ring (R) group

4. LINKAGE OF AMINO ACIDS
In protein , the amino acids link up in such a way that the amino group of one amino acid is join to the carboxyl group of the adjacent one with the loss of water molecule for each linkage as a byproduct .
The amino group contribute hydrogen and the carboxyl group contribute hydroxyl group (-OH) to water.
The covalent bond joining the two amino acid unit by –NH-CO linkage is called Peptide Bond . It is formed by process of condensation ( Dehydration ) i.e loss of water .
A chain of two amino acid is called Dipeptide . A chain of three amino acid is called Tripeptide , of a few ( less then 30 ) , Amino acid an Oligopeptide and of many ( more then 30 ) , Amino acid are Polypeptide.

5. Physical properties of amino acids
Solubility
Generally soluble in water, acids ,alkalis
Sparingly soluble in organic solvents
High melting point
Possess higher melting point
Melt with decomposition
Presence of asymmetric carbon(Chiral)
Glycine is optically inactive , all other the amino acids contain at least one asymmetric carbon atom and are optically active
They exist in d and l forms.
Zwitter ion
Amphoteric
Amino acids have both acidic and basic properties.

6. FUNCTION
Essential
LYSINE : They are involved in the synthesis of enzymes and other hormones .
HISTIDINE : Helps in the production and synthesis of both RBC and WBC .
LEUCINE : Its promotes the synthesis of growth hormones.
METHIONINE : Helps in a maintaining a good and healthy skin .
ISOLEUCINE :Plays a vital role in synthesis of hemoglobin and its major component of RBC .
VALINE : Helps in growth of muscles .
Non- essential
TYROSINE : It plays a vital in a production of T3 and T4 thyroid hormones .
ARGENINE : It promotes the biosynthesis of protiens .
GLYCINE : It acts as a neurotransmitter and plays a vital role in healing wounds .
CYSTENINE : Provides resistance to our body and inhibts the growth hairs , nails and etc .
ALANINE : Helps in removal of toxic from our body .

7. CLASSIFICATION Based On Nature Of Amino Acids
Based on special structure
Based on nutritional requirement
Based on polarity

8. Based on nature
ACIDIC AMINO ACIDS : These contain one amino group and two carboxyl group per molecule . These are called as monoamino-dicarboxylic amino acids . Example – Aspartic acid, Glutamic acid.
BASIC AMINO ACIDS : These contain two amino group and one carboxyl group per molecule. These are called as diamino- monocarboxylic amino acids . Example – Lysine , Arginine.
NEUTRAL AMINO ACIDS : These have one amino group and one carboxylic group per molecule . These are called as monoamino- monocarboxylic amino acids. Example – Glycine, Valine .

9. Based on special structure
SULPHUR CONTAINING AMINO ACIDS : These amino acids contain sulphur.
Example: Methionine, Cysteine .
ALCOHOLIC AMINO ACIDS : These amino acids contain alcoholic group.
Example – Serine , Threonine , Tyrosine.
AROMATIC AMINO ACIDS: These amino acids contain phenyl rings.
Example – Phenylalanine , Tryptophan
HETROCYCLIC AMINO ACIDS : These amino acids contain heterocyclic ring.
Example – Proline

10. Based on nutritional requirement
ESSENTIAL AMINO ACIDS : There are few amino acids that cannot be synthesized by body.
Examples: Phenylalanine, Valine, Leucine, Lysine, Methionine , Histidine.
NON ESSENTIAL AMINO ACIDS : There are few amino acids which are easily bio synthesized by our body.
Examples: Alanine , Cysteine, Cysteine, Glutamine, Glycine, Glutamate, Arginine, Tyrosine , Serine , Asparagine, Aspartic acid, Proline.

11. Based on polarity POLAR AMINO ACIDS NON-POLAR AMINO ACIDS UNCHARGED:
Serine,Threonine,Glutamine,Asparagine, Cysteine.
CHARGED:
Positively charged: Arginine, Lysine, Histidine.
Negatively charged: Glutamate, Aspartate.
ALIPHATIC:
Proline,Valine,Leucine,Isoleucine,Methionine.
AROMATIC:
Tyrosine, Phenylalanine, Tryptophan.

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