For Medical & Non Medical Students

1. Chemistry
Of
Amino Acids
By
N.Santhosh Kumar
Asst.Professor
Department of Biochemistry
SIMS & RH

2. Buffer like function
( Histidine)
Detoxification functions
(Gly, Cysteine & Methionine)
Transport and storage form
of ammonia: Glutamine
Formation of Glucose
(Glucogenic amino acids)
Formation of proteins
Imp role in certain enzyme
activity
Dietary source of nitrogen
Dietary source of Sulfur
Produces peptide hormones
Involved in nitrogenous
bases
Source of energy
Forms Biological important
compounds

3. Amino acids are an organic compounds containing 2
functional groups.
Amine group (- NH2)- Basic
Carboxyl group (COOH) - Acidic in nature
R- Side chain is most imp in determining reactivity of amino acids

4. • In the physiological pH range, both carboxylic and
amine groups are completely ionized

5. 20 of the proteinogenic L- a.a’s are encoded
directly by triplet codons in the universal
genetic code - standard amino acids.
21st a.a’s (Selenocysteine),
22nd a.a’s (pyrrolysine) are incorporated in
to proteins by unique synthetic mechanism
(UGA & UAG stop codon)
Found in some antibiotics produced by
micro-organism &in bacterial cell walls
D-Serine (fore –brain) & D-Aspartic acid
(brain periphery): activates neuro-
transmitter receptors

6. Non proteinogenic amino acids
• Not produced directly
• formed by post-translational modification (essential for
the function or regulation of a protein activation)
– Carboxylation of glutamate - better binging of ca+
– Collagen contains OH- Proline & OH- lysine

8. Some NPAA’s are not found in proteins
• 5-OH tryptophan – precursor of serotonin
• 3,4-Dihydroxy phenylalanine (DOPA) – Melanin &
neurotransmitter
• Carnitine
• β -amino isobutyric acid - catabolism of thymine & valine
• Ornithine & Citrulline
• GABA : Glutamic acid – act as an Neurotransmitter

9. Beta amino acids:
• β-alanine used in plants and microorganism in the
synthesis of pantothenic acid (B5) as a compound of Co-A

10. Sources
Beans, Nuts, Seeds,
Milk, Eggs,
Meat & Sea foods

11. Classification
Of
Amino Acids

12. • According to the Charge
Dietary requirement
Metabolic fate
• Ionic charge of the side chain, amino acids are grouped as
electrically Neutral amino acids ,
Acidic amino acids or
Basic amino acids

13. I. Neutral amino acids
Aliphatic amino acids
1. Simple aliphatic amino acid
Glycine : simplest a.a & has no asymmetric carbon atom &
no optical activity.

14. 2. Branched chain amino acid

15. 3. Hydroxyl group containing amino acids

16. 4. Sulfur containing amino acids
Thiol (-SH )
group
Disulfide (-S-S- ) group
Sulfur (-CH3-S- ) group

17. Aromatic amino acid
Benzene group
Indole ring
Phenol group

18. II. Acidic amino acids
Amides of the
Acidic amino acids

19. III. Basic amino acids
(aliphatic / heterocyclic rings)

20. Imino acid
It does not contain a primary alpha amino group (NH2) but
has a secondary amino group (NH-)
4- OH proline: incorporated in the peptide chain during collage
synthesis
Pyrrolidine Group

21. II. NUTRITIONAL CLASSIFICATION

22. Essential amino acids Semi–Essential
amino acids
Non Essential amino
acids
cannot be synthesized by
the body & to be taken in
food for normal growth.
- It can be synthesized
by adults & not by
growing children
- These amino acids
are required by
growing children
- Can be produced from
endogenous metabolites
Eg: Arginine,
Valine, Leucine,
Isoleucine, Lysine,
Methionine, Histidine,
Phenylalanine,
Threonine, Tryptophan
Eg: Arginine &
Histidine
E.g. Glycine, Alanine,
Serine, Proline,
Tyrosine, Cysteine,
Glutamic acid,
Aspartic acid,
Glutamine & Aspargine

23. Based on Metabolic Fate
All the amino acids carbon
skeleton enters either
Formation of Glucose or Fat/
Ketone bodies
+ Ammonia

24. Glucogenic amino
acids
Ketogenic amino
acids
Both Glucogenic &
ketogenic amino acids
Which can be
converted into
glucose.
Which can be
converted into
lipids.
Which can be converted
to both types of
compounds.
Glucose & lipids
Eg: Glycine, Alanine,
valine, Proline, Serine,
Aspargine, Arginine,
Glutamine, Cysteine,
Threonine, Histidine ,
Methionine , Glutamic
acid, Aspartic acid
Eg. leucine Eg. Isoleucine, lysine,
Phenylalanine,
Tyrosine and
Tryptophan

25. PROPERTIES OF AMINO ACIDS:
• Colorless, Tasteless, Crystalline substances.
• Generally all amino acids are soluble in water but
insoluble in non-polar organic solvents.
• Exert acid-base behavior, Zwitter ion formation and
buffering activity.
• The pH at which amino acids carries no net charge is
known as iso-electric point

26. Zwitter ion / Dipolar ion:
• It is a neutral molecule with positive & negative electrical charge at
different locations within the same molecule.
• α-carboxylic (COOH) group is ionized, becomes negatively charged
anion (COO¯)
• The α–amino (NH2) group is protonated to from a positively charged
cation (NH4⁺).

27. Isoelectric pH
• In acidic solution they are cationic in form (positively charged)
• In alkaline solution they behave as anions (negatively charged)
• The pH at which amino acids carries no net charge is known as iso-
electric point or iso-electric pH (pI).
i.e. [RCOO-] = [RNH3
+]
e.g. Isoelectric point for glycine pH is 6.0, Aspartate (3.0),
Lysine (9.8), Arginine (10.8)
H⁺acid H
Cation (at acidic pH) zwitter ion isoeletric pH anion (at alkaline pH)

28. Biological Important Compounds
Formed By Amino Acids

29. Amino acid Compounds
Tyrosine Hormones: (Catecholamines & Thyroxine)
Skin pigments (Melanin)
Tryptophan Niacin (vitamin) , Melatonin (hormone)&
Serotonin (neurotransmitter)
Glycine Heme
Glycine & Cys Bile salts
Glu, Cys &Gly Glutathione
Glycine , Arg & Met Creatine
Gly, Asp & Glu Purines and pyrimidine bases
Beta alanine Coenzyme -A
Histidine Histamine
Glutamic acid GABA: neurotransmitter

30. FORMATION
OF
PEPTIDE BONDS

32. • All the amino acids are held
together in a protein by covalent
peptide bonds.
• When the carboxyl group of an
amino acid combines with the
amino group (NH2) of another
amino acid to form peptide bond
& produces a molecule of water
• Two amino acids joined by a
peptide bond (-CO-NH-) are
called a dipeptide.
• Amino acid is read from N to the
C- terminus

34. Peptide Biological Importance
Aspartame
(Dipeptide)
- Sweeter than sucrose. Used as a low caloric
artificial sweetener in soft drink
Glutathione
(Tripeptide)
- It exists in reduced or oxidized state.
- Maintains RBC membrane structure and integrity.
- Protects Hb from getting oxidized by agent
- Involved in the transport of a.a’s in intestine
- Involved in the detoxification process
Oxytocin
(Nano peptide)
- Secreted by posterior pituitary gland
- It causes contraction of uterus.
Vasopressin
(ADH)
- It stimulates kidneys to retain water.
- Increase the blood pressure

35. Next class
CA-02: PEPTIDES & IT’S ROLE IN THE
BODY

36. GOOD MORNING
There Is No Fixed Matra For Success
Except That You Have To Learn
To Conquer Your Fears & Not Let Failure
Or Negativity Demotivate You