269256 amino-acids-peptides-and-proteins
Transcript of 269256 amino-acids-peptides-and-proteins
![Page 1: 269256 amino-acids-peptides-and-proteins](https://reader036.fdocuments.us/reader036/viewer/2022081507/55501bbbb4c905af648b4f95/html5/thumbnails/1.jpg)
www.Examville.comOnline practice tests, live classes, tutoring, study guides
Q&A, premium content and more.
![Page 2: 269256 amino-acids-peptides-and-proteins](https://reader036.fdocuments.us/reader036/viewer/2022081507/55501bbbb4c905af648b4f95/html5/thumbnails/2.jpg)
Amino Acids, Peptides and Proteins
![Page 3: 269256 amino-acids-peptides-and-proteins](https://reader036.fdocuments.us/reader036/viewer/2022081507/55501bbbb4c905af648b4f95/html5/thumbnails/3.jpg)
The Proteins speak:
“We are the basis of structureand function of life;
Composed of twenty amino acids,the building blocks;
Organized into primary, secondary, tertiary
and quaternary structure;Classified as simple, conjugated
and derived proteins.”
![Page 4: 269256 amino-acids-peptides-and-proteins](https://reader036.fdocuments.us/reader036/viewer/2022081507/55501bbbb4c905af648b4f95/html5/thumbnails/4.jpg)
AMINO ACIDS
- group of organic compounds containing two functional groups:
amino group (-NH2) basiccarboxyl group (-COOH) acidic
![Page 5: 269256 amino-acids-peptides-and-proteins](https://reader036.fdocuments.us/reader036/viewer/2022081507/55501bbbb4c905af648b4f95/html5/thumbnails/5.jpg)
General Structure of Amino Acids
H H
R C COOH R C COOH
NH2 NH3
General Structure Exists as ion
![Page 6: 269256 amino-acids-peptides-and-proteins](https://reader036.fdocuments.us/reader036/viewer/2022081507/55501bbbb4c905af648b4f95/html5/thumbnails/6.jpg)
⍺ - amino acids
aminogroups – attached to
thecarboxyl same carbon Atom
⍺ - carbon atom binds to a side chain represented by R (different for
each of the 20 amino acids found in proteins)
Ionized forms how they exist
![Page 7: 269256 amino-acids-peptides-and-proteins](https://reader036.fdocuments.us/reader036/viewer/2022081507/55501bbbb4c905af648b4f95/html5/thumbnails/7.jpg)
Classification of Amino Acids based on polarity
of the R group
4 groups
Polarity reflects the functional role of AA in protein structure
![Page 8: 269256 amino-acids-peptides-and-proteins](https://reader036.fdocuments.us/reader036/viewer/2022081507/55501bbbb4c905af648b4f95/html5/thumbnails/8.jpg)
1. Non-polar AA
hydrophobic (water hating)No charge on the ‘R’ groupExamples are:
Alanine MethionineLeucine
PhenylalanineIsoleucine
TryptophanValine Proline
![Page 9: 269256 amino-acids-peptides-and-proteins](https://reader036.fdocuments.us/reader036/viewer/2022081507/55501bbbb4c905af648b4f95/html5/thumbnails/9.jpg)
3. Polar AA with (+) ‘R’ group
carries (+) charge Examples:
Histidine Arginine Lysine
4. Polar AA with (-) ‘R’ group
• carries (-) charge• Examples:
Glutamic Acid Aspartic Acid
![Page 10: 269256 amino-acids-peptides-and-proteins](https://reader036.fdocuments.us/reader036/viewer/2022081507/55501bbbb4c905af648b4f95/html5/thumbnails/10.jpg)
2. Polar AA with no charge on ‘R’ group
no charge on the ‘R’ group possess groups hydroxyl
sulfhydrylamide
participate in hydrogen bonding of protein structure
Examples:Asparagine Glycine
Cysteine Tyrosine Serine Threonine Glutamine
![Page 11: 269256 amino-acids-peptides-and-proteins](https://reader036.fdocuments.us/reader036/viewer/2022081507/55501bbbb4c905af648b4f95/html5/thumbnails/11.jpg)
A.Physical Properties
1. Solubility - soluble in water and insoluble in organic solvents
2. Melting Points - melt at higher temperatures often 200°C
3. Tastesweet (Gly, Ala, Val)tasteless (Leu)bitter (Arg, Ile)Sodium Glutamate – salt of Glutamic Acid – flavoring
agent
![Page 12: 269256 amino-acids-peptides-and-proteins](https://reader036.fdocuments.us/reader036/viewer/2022081507/55501bbbb4c905af648b4f95/html5/thumbnails/12.jpg)
4. Optical Properties
- Assymetric a carbon atom is attached to 4 different groups
exhibiting optical isomerism
4 distinct groups R H - held by an
COOH ⍺-carbon NH3໋
![Page 13: 269256 amino-acids-peptides-and-proteins](https://reader036.fdocuments.us/reader036/viewer/2022081507/55501bbbb4c905af648b4f95/html5/thumbnails/13.jpg)
All AA except Glycine possess optical isomers due to asymmetric ⍺-carbon atom
Some AA (Isoleucine, Threonine) 2nd asymmetric carbon
![Page 14: 269256 amino-acids-peptides-and-proteins](https://reader036.fdocuments.us/reader036/viewer/2022081507/55501bbbb4c905af648b4f95/html5/thumbnails/14.jpg)
D- and L- forms of AA based onthe structure of glyceraldehyde
CHO CHO
H C OH OH C H
CH2OH CH2OH
D-Glyceraldehyde L-Glyceraldehyde
![Page 15: 269256 amino-acids-peptides-and-proteins](https://reader036.fdocuments.us/reader036/viewer/2022081507/55501bbbb4c905af648b4f95/html5/thumbnails/15.jpg)
R R
H C NH2 H2N C H
COOH COOH
D-Amino Acid L-Amino Acid
The proteins are composed of L-⍺ amino acids
![Page 16: 269256 amino-acids-peptides-and-proteins](https://reader036.fdocuments.us/reader036/viewer/2022081507/55501bbbb4c905af648b4f95/html5/thumbnails/16.jpg)
5. Amino acids as ampholytes
can donate a proton or accept a
proton
AA contain both acidic (-COOH) and basic (-NH2) groups
![Page 17: 269256 amino-acids-peptides-and-proteins](https://reader036.fdocuments.us/reader036/viewer/2022081507/55501bbbb4c905af648b4f95/html5/thumbnails/17.jpg)
Zwitterion or dipolar ion:
Zwitter from German word – means
“hybrid”
Zwitter ion (or dipolar ion) a hybrid molecule containing
(+) and (-) ionic groups
![Page 18: 269256 amino-acids-peptides-and-proteins](https://reader036.fdocuments.us/reader036/viewer/2022081507/55501bbbb4c905af648b4f95/html5/thumbnails/18.jpg)
AA rarely exist in a neutral form with free carboxylic (-COOH) and free Amino (-NH2) groups
Strongly acidic pH (low pH) AA (+) charged (cation)
Strongly alkaline pH (high pH) AA (-) charged (anion)
Each AA has a characteristic pH (e.g. Leucine, pH – 6.0), at which it carries both (+) and (-) charges and exist as zwitterion
![Page 19: 269256 amino-acids-peptides-and-proteins](https://reader036.fdocuments.us/reader036/viewer/2022081507/55501bbbb4c905af648b4f95/html5/thumbnails/19.jpg)
Existence of an amino acid as Cation, Anion and Zwitterion
H
H໋ R C COOH H໋
NH2
H Amino Acid H
R C COOH R C COO ¯
NH3 ໋ H NH2
Cation H໋ H໋ Anion (low pH) R C COO ¯ (high pH)
NH3 ໋Zwitterion
(Isoelectric pH)
![Page 20: 269256 amino-acids-peptides-and-proteins](https://reader036.fdocuments.us/reader036/viewer/2022081507/55501bbbb4c905af648b4f95/html5/thumbnails/20.jpg)
B. Chemical Properties
General Reactions mostly due to the 2 functional groups
Reactions due to - COOH group
1. AA from salts (-COONa) with bases and esters (-COOR’) with alcohols
2. Decarboxylation - AA undergo decarboxylation to produce corresponding amines
![Page 21: 269256 amino-acids-peptides-and-proteins](https://reader036.fdocuments.us/reader036/viewer/2022081507/55501bbbb4c905af648b4f95/html5/thumbnails/21.jpg)
3. Reaction with Ammonia
- the carboxyl group of dicarboxylic AA reacts with NH3 to form amide
Asparatic Acid + NH3 AsparagineGlutamic Acid + NH3 Glutamine
![Page 22: 269256 amino-acids-peptides-and-proteins](https://reader036.fdocuments.us/reader036/viewer/2022081507/55501bbbb4c905af648b4f95/html5/thumbnails/22.jpg)
Reactions due to -NH2 group
4. The Amino groups behave as bases and combine with acids (e.g. HCl) to form salts (-NH3 + Cl¯)
5. Reaction with NINHYDRIN- the ⍺-AMINO ACIDS react with
Ninhydrin to form a purple, blue or pink colour complex (Ruhemann’s purple)
![Page 23: 269256 amino-acids-peptides-and-proteins](https://reader036.fdocuments.us/reader036/viewer/2022081507/55501bbbb4c905af648b4f95/html5/thumbnails/23.jpg)
Amino acid + Ninhydrin Keto acid + NH3 + CO2 + Hydrindantin
Hydrindantin + NH3 + Ninhydrin Ruhemman’s purple
Ninhydrin reaction – quantitative determination of AA and proteins
![Page 24: 269256 amino-acids-peptides-and-proteins](https://reader036.fdocuments.us/reader036/viewer/2022081507/55501bbbb4c905af648b4f95/html5/thumbnails/24.jpg)
6. Colour reactions of Amino Acids
- AA can be identified by specific colour reactions
Color Reactions of proteins / AA
Reaction Specific group or AA
1. Buiret Reaction Two peptide linkages2. Ninhydrin Reaction ⍺-Amino acids3. Xanthoproteic Reaction Benzene ring of
aromatic AA (Phe, Tyr, Trp)
4. Million’s reaction Phenolic Group (Tyr)5. Hopkins – Cole Reaction Indole Ring (Trp)
![Page 25: 269256 amino-acids-peptides-and-proteins](https://reader036.fdocuments.us/reader036/viewer/2022081507/55501bbbb4c905af648b4f95/html5/thumbnails/25.jpg)
6. Sakaguchi Reaction Guanidino Group (Arg)
7. Nitroprusside Reaction Sulfhydryl groups (Cys)
8. Paulys’ test Imidazole ring (His)
9. Sulfur test Sulfhydryl groups (Cys)
10. Folin – Coicalteau’s Phenolic groups test (Tyr)
![Page 26: 269256 amino-acids-peptides-and-proteins](https://reader036.fdocuments.us/reader036/viewer/2022081507/55501bbbb4c905af648b4f95/html5/thumbnails/26.jpg)
7. Transamination
- important reaction in AA metabolism
- transfer of an amino group from an amino acid to a keto acid to form a new AA
8. Oxidative deamination
- AA undergo oxidative deamination to liberate free ammonia
![Page 27: 269256 amino-acids-peptides-and-proteins](https://reader036.fdocuments.us/reader036/viewer/2022081507/55501bbbb4c905af648b4f95/html5/thumbnails/27.jpg)
www.Examville.com Online practice tests
Live classes Tutoring Study guides Q&A Premium content and more.