Amino Acids (building blocks of protein).pptx

Classification on the bases of polarity
1. Non-polar amino acid with
Glycine, Alanine, Valine, Methionine, Leucine, Isoleucine, Proline, Phenylalanine, Tryptophan.
2. Polar Amino Acids
I. Negatively charge amino acid
Aspartic acid, Glutamic Acid
II. Positively charge amino acid
Lysine, Arginine, Histidine.
III. Neutral amino acid
Serine, Threonine, Asparagine, Glutamine, Cysteine, Tyrosine
Polarity of amino acid
Tyr>Ser>Asp>Glu>Asn>Gln>Arg
Non-polarity of amino acid
Phy>Ala>Val>Gly>Leu>Cys

Which amino acid is hydrophobic?
Which amino acid is hydrophilic?
Which of the amino acids residues are most likely to be found in the interior of the water soluble protein?

Classification of amino acids
Neutral amino acids
Glycine-Gly-G
Amino acid with smallest side chain
Most abundant in collagen
No chiral carbon (No optical activity)
Sweet in taste
Neurotransmitter inhibitor

2. Alanine-Ala-A
Amino acid with methyl group
Most abundant amino acid in protein

3. Valine-Val-V
Branched at β-carbon
Amino Acid with two chiral carbon


4. Leucine-Leu-L
Branched at γ-carbon

5. Isoleucine-Ile-I
Amino acid with 2 chiral carbon

6. Serine-Ser-S
Help in the synthesis of muscle protein
Phosphorylation in cell signaling

7. Threonine-Thr-T
Branched at β-carbon
Amino Acid with two chiral carbon

8. Proline-Pro-P
A cyclic imino acid
Present in α-helix and β-turn
Acidic amino acids
9. Aspartic acid-Asp-D
Amino acid with β-carbonyl group
Frequently present on N-terminus of α-helix

10. Glutamic Acid-Glu-E

Amide form of acidic amino acids
11. Asparagine-Asn-N

12. Glutamine-Gln-Q

Sulphur containing amino acids
13. Cysteine-Cys-C
Amino acid with thiol group
Involve in disulphide bond
14. Methionine-Met-M
First amino acid in protein
Second least present in protein
Basic amino acids
15. Histidine-His-H
Amino acid with imidazole ring
Having buffering capacity
Help in Immune response

16. Lysine-Lys-K and 17. Arginine-Arg-R
Rich in histone protein
Lysine has butyl-ammonium side chain
Aromatic ring acidic amino acids
18. Phenylalanine-Phe-F
Maximum absorption at 280nm
Naturally present in breast milk
Related with phenylketonuria
19. Tyrosine-Tyr-Y
Maximum absorption at 280nm
Phosphorylation in cell signaling
20. Tryptophan-Trp-W
Least present in protein, indole ring amino acid
General Characters of amino acids
There are more than 500 amino acids present in the nature.
Only 20+2 participate in the formation proteins.
Amino acids have N-terminus, C-terminus and R-group in their structure.
Average mass of an amino acid residue is ~ 110 Da.
Selenocystine is 21st amino acid, analog of cysteine, having antioxidant acitivity.
Pyrolysisne is not present in human.
Amino acids are made visible on the chromatogram by the treatment with ninhydrin.
Non-polar amino acid are found mostly in the core of protein.


Acid base characters of amino acids
pK can be defined as the pH at which the acid is 50% dissociated.
If- pK=pH+1………….. Acid is 91% dissociated.
pK=pH+2………….. Acid is 99%

1. A m i n o A c i ds

2. Contents Amino Acids General Characters Structure and Classification Acid Base Characters of Amino Acids Peptides Proteins Structure and configuration Chemical bond involve in protein structure Classification Protein Sequencing

3. Amino Acid General Structure All amino acids are α -amino acid. All proteinic amino acids have same structure except proline

4. Polar Non-Polar Ala Ile Val Gly Met Phe Pro Trp Leu Acidic Neutral Basic Asp Glu Tyr Cys Ser Asn Gln Thr Arg Lys His Classification of A m i n o A c i d

5. Classification on the bases of polarity 1. Non-polar amino acid with Glycine, Alanine, Valine, Methionine, Leucine, Isoleucine, Proline, Phenylalanine, Tryptophan. 2. Polar Amino Acids I. Negatively charge amino acid Aspartic acid, Glutamic Acid II. Positively charge amino acid Lysine, Arginine, Histidine . III. Neutral amino acid Serine, Threonine, Asparagine, Glutamine, Cysteine, Tyrosine Polarity of amino acid Tyr>Ser>Asp>Glu>Asn>Gln>Arg Non-polarity of amino acid Phy>Ala>Val>Gly>Leu>Cys

6. Which amino acid is hydrophobic? Which amino acid is hydrophilic? Which of the amino acids residues are most likely to be found in the interior of the water soluble protein?

7. Classification of amino acids Neutral amino acids Glycine- Gly -G Amino acid with smallest side chain Most abundant in collagen No chiral carbon (No optical activity) Sweet in taste Neurotransmitter inhibitor 2. Alanine-Ala-A Amino acid with methyl group Most abundant amino acid in protein 3. Valine-Val-V Branched at β -carbon Amino Acid with two chiral carbon

8. 4. Leucine- Leu -L Branched at γ -carbon 5. Isoleucine-Ile-I Amino acid with 2 chiral carbon 6. Serine- Ser -S Help in the synthesis of muscle protein Phosphorylation in cell signaling 7. Threonine- Thr -T Branched at β -carbon Amino Acid with two chiral carbon 8. Proline -Pro-P A cyclic imino acid Present in α -helix and β -turn

9. Acidic amino acids 9. Aspartic acid-Asp-D Amino acid with β -carbonyl group Frequently present on N-terminus of α -helix 10. Glutamic Acid- Glu -E Amide form of acidic amino acids 11. Asparagine- Asn -N 12. Glutamine- Gln -Q Sulphur containing amino acids 13. Cysteine- Cys -C Amino acid with thiol group Involve in disulphide bond 14. Methionine-Met-M First amino acid in protein Second least present in protein

10. Basic amino acids 15. Histidine-His-H Amino acid with imidazole ring Having buffering capacity Help in Immune response 16. Lysine-Lys-K and 17. Arginine- Arg -R Rich in histone protein Lysine has butyl-ammonium side chain Aromatic ring acidic amino acids 18. Phenylalanine- Phe -F Maximum absorption at 280nm Naturally present in breast milk Related with phenylketonuria 19. Tyrosine-Tyr-Y Maximum absorption at 280nm Phosphorylation in cell signaling 20. Tryptophan- Trp -W Least present in protein, indole ring amino acid

11. General Characters of amino acids There are more than 500 amino acids present in the nature. Only 20+2 participate in the formation proteins. Amino acids have N-terminus, C-terminus and R-group in their structure. Average mass of an amino acid residue is ~ 110 Da. Selenocystine is 21 st amino acid, analog of cysteine, having antioxidant acitivity . Pyrolysisne is not present in human . Amino acids are made visible on the chromatogram by the treatment with ninhydrin . Non-polar amino acid are found mostly in the core of protein. Classification on the bases availability in the human body 1. Essential amino acids Leucine, Isoleucine, Lysine, Threonine, Methionine, Phenylalanine, Valine, Tryptophan, Histidine (conditionally essential) 2 . Non-essential amino acids Glycine, Alanine, Valine, Arginine, Serine , Asparagine , Glutamine, Cysteine, Tyrosine, Aspartic acid, Glutamic Acid.

12. Acid base characters of amino acids pK can be defined as the pH at which the acid is 50% dissociated. If- pK =pH+1………….. Acid i s 91% dissociated . pK =pH+2 ………….. Acid is 99% dissociated . pK =pH-1………….. Acid is 9% dissociated . pK =pH-2 ………….. Acid is 1 % dissociated . pI (isoelectric point) is the pH at which net charge of amino acid is zero. (total number of positive charge equal to the total number of negative charge). Calculation of For Acidic amino acids: Calculation of For basic amino acids Calculation of    

13. Nature of amino acid at different pI If pI < 7 then the amino acid is acidic pI ~ 7 then the amino acid is neutral pI > 7 then the amino acid is basic If the p H of the solution is equal to the pI then net charge of amino acid or protein is zero. If the p H of the solution is lower to the pI then net charge of amino acid or protein is positive. If the p H of the solution is higher to the pI then net charge of amino acid or protein is negative. Important point: Aspartate has the smallest pI value Arginine has the largest pI value Amino acids tend to be least soluble in water at their isoelectric point. Net charge: +1 0 -1    

14. Peptides α -carboxyl group of one or first amino acid react with α -amino group of other or second amino acid, a dipeptide is formed with release of water molecule. A peptide bond is a covalent bond b/w carbonyl carbon and an imino nitrogen also k/n as amide bond. The peptide bond in peptide and protein has been found to possess a partial double bond, polar, planar and mostly trans The average molecular weight of amino acid residue in the peptide has been taken 110. Molecular weight of the peptide= (no. of aa residues X average residue weight)- 18X number of water molecules removed

15. Some oligo-peptides Aspartame  ( APM ): is a  methyl ester of the aspartic acid/phenylalanine dipeptide . It is used as artificial sweetener, 200 time more sweet that sugar. Glutathione: it is tripeptide, made-up of Glu-Cys-Gly . γ -carbonyl group of Glu is i nvolved in the peptide bond formation. It control oxidative damage of RBC. Gramicidin: A circular deca -peptide. A bacterial synthesized antibiotic. Vasopressin and oxytocin: made-up of nine amino acids with di- sulphide bonds, secreted by pituitary gland. Oxytocin natural hormone that causes the uterus to contract and used to induce labor or strengthen labor contractions during childbirth, and to control bleeding after childbirth. Vasopressin help in the retention of water from urine by kidney and also involve in higher of blood pressure. Methionine enkephalin : penta - peptide, inhibit sense of pain. Angiotensin II : octapeptide , stimulate the release of aldosterone from the adrenal gland. Substance P: decapeptide , k/n as neurotransmitter .