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AMINO
ACID
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.
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
LINKAGE OF AMINO ACIDS
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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.
Physical properties of amino acids
Solubility
High melting point
Presence of asymmetric
carbon(Chiral)
• Generally soluble in water, acids ,alkalis
• Sparingly soluble in organic solvents
• Possess higher melting point
• Melt with decomposition
• 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.
FUNCTION
Nonessential
Essential
VALINE : Helps in growth of
muscles .
ISOLEUCINE :Plays a vital
role
in
synthesis
of
hemoglobin and its major
component of RBC .
METHIONINE : Helps in a
maintaining a good and
healthy skin .
LEUCINE : Its promotes the
synthesis of growth hormones.
LYSINE : They are involved
in the synthesis of enzymes
and other hormones .
HISTIDINE : Helps in the
production and synthesis of
both RBC and WBC .
ALANINE : Helps in removal
of toxic from our body .
CYSTENINE : Provides
resistance to our body and
inhibts the growth hairs , nails
and etc .
GLYCINE : It acts as a
neurotransmitter and plays a
vital role in healing wounds .
ARGENINE : It promotes the
biosynthesis of protiens .
TYROSINE : It plays a vital
in a production of T3 and T4
thyroid hormones .
CLASSIFICATION
Based On Nature Of Amino Acids
Based on special structure
Based on nutritional requirement
Based on polarity
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 .
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
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.
Based on polarity
POLAR AMINO ACIDS
NON-POLAR AMINO ACIDS
• UNCHARGED:
• ALIPHATIC:
Serine,Threonine,Glutamine,Asparagine,
Cysteine.
Proline,Valine,Leucine,Isoleucine,Methio
nine.
• CHARGED:
• AROMATIC:
a) Positively charged: Arginine, Lysine,
Histidine.
b) Negatively charged: Glutamate,
Aspartate.
Tyrosine, Phenylalanine, Tryptophan.
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