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Amino acid structure classification and properties

This document discusses the structure, classification, and properties of amino acids. It begins by defining amino acids as the building blocks of proteins. It then covers amino acid structure, various classification systems including based on polarity and R groups, and essential vs. non-essential amino acids. The document also discusses the physical, chemical, and biological properties of specific amino acids like alanine, valine, leucine, and others. It provides information on isoelectric points and gives examples of biochemical tests used to identify different amino acids.

Science◦
Amino acid structure classification and properties U.DEEPALAKSHMI 1 M.Sc MICROBIOLOGY
What is amino acid? Amino acids are the building blocks of peptides and proteins. Amino acids are monomer of protein . The first amino acid discovered was Asparginine in 1806.
Amino acid structure: while they all have common elements of an amine group, a carboxyl group and a side chain.
Amino acid classification: Based on their R group and polarity. Based on their nutrition. Nonstandard protein amino acid. Non protein amino acid.
1.Classification based on polarity: Non polar amino acid. Polar uncharged amino acid. Polar positive charged amino acid. Polar negative charged amino acid.
NON POLAR AMINO ACID:
valine Tryptophan Proline
Polar uncharged amino acid: serine Threonine Tyrosine
Polar positive charged amino acid:
Polar negative charged amino acid:
Classification based on their R group: 1.Simple amino acid- Glycine , Alanine, valine, Leucin, isoleucin. 2.Hetero cyclic amino acid- Histidine, Proline. 3.Aromatic amino acid- Phenylalanine, Tryptophan , Tyrosine. 4.sulphar contain amino acid-Methionine, Cysteine.
5.Hydroxyil group contain amino acid- Serine, Threonine, Tyrosine. 6.Acitic amino acid-Aspartic acid, Glutamic acid. 7.Basic amino acid-Lysine, Histidine, Arginine.
2.Classification based on their nutrition: Essential amino acid. Non essential amino acid.
Essential amino acid: Essential amino acids cannot be made by the body. As a result, they must come from food. There are nine
Valine. Phenylalanine. Leucin. Isoleucin. Threonine. Tryptophan. Methionine. Lysine. Histidine.
Non essential amino acid: Non essential amino acids are produced by human body either from essential amino acid or from normal proteins break down.
Asparginine. Alanine. Arginine. Aspartic acid. Cysteine. Serine. Glutamic acid. Glutamine. Proline. Glycine. Tyrosine.
3.Non standard protein amino acid: These have a limited distribution but may be present in high amounts in a few proteins. As an example hydroxyproline has a limited distribution in nature but constitutes as much as 12% of the composition of collagen an important structural protein of animals.
Hydrolysine is also a important component of collagen where it accounts for about 1% of the total amino acids. N- methyllisne is found in myosin, a contractile protein of muscle. Another important gamma- carboxyglutamate which is found in the blood clotting protein.
N-Methyl lysine
4.Non protein amino acid: The important non protein amino acids, which play metabolic roles such as L- ornithine, L- citrulin, creatinine , and gamma amino butyrate. L-ornithine and L-citrulin occur in free state in the animal tissue and are metabolic intermediates in urea cycle.
The quaternary amine creatinine, a derivative of Glycine plays an important role in the energy storage process in vertebrates. Gamma amino butyrate is found in free from in the brain.
Citrulin
Properties of amino acid: There are 3 properties such as Physical properties. Chemical properties. Biological properties.
Physical properties: 1.color and taste-proteins are colorless and usually tasteless these are homogenous and crystalline. Tasteless-tyrosine. Sweet-Glycine, Alanine. Bitter-Arginine.
2.Shape and size: A . Globular protein-These are spherical in shape and occur in mainly plants in leaf cells. EX: PEPSIN. B. Fibrillar protein-these are thread like structure occur in animal muscles. EX:FIBRINOGEN and MYOSIN. SIZE: 1.Hemoglobin-55 A. 2.collagen-3000A.
3.Molecular weight: EX:Albumin-65000.,Fibrinogen-400000. 4.Amphoteric nature: The proteins are amphoteric i,e they act as both acid and alkali. ISOELECTRIC POINT is the PH value at which the number of cations is equal to anions. the net electric charge of a protein is always 0.
Chemical properties: Reaction based on NH2 group. Reaction based on COOH group. Reaction based on NH2 and COOH group. Reaction based on R group.
Reaction based on R group: Folins test : blue color develops with phosphomolybdotungustic acid in alkaline solution due to the presence of phenol group. This test specific for tyrosine. Sakaguchi test: red color develops with alpha naphthol and sodium hypochlorite. The test detected for Arginine.
Biuret test :compounds containing peptide bonds produce a purple color when treated with an alkaline 0.2% copper sulfate solution .this reaction is known as biuret reaction. Reaction involving SH group: NITROPRUSSIDE TEST – red color develops with sodium nitroprusside in dilute ammonium hydroxide .this test specific for Cysteine.
Electro chemical properties: The isoelectric point (pI, pH(I), IEP), is the pH at which a particular molecule carries no net electrical charge or is electrically neutral in the statistical mean. The standard nomenclature to represent the isoelectric point is pH(I), although pI is also commonly called.
ALANINE: PI= PK1+PK2/2 =2.34+9.69/2 =12.03 PI =6.01 ARGININE: PI=PK2+PK3/2 =9.04+12.48 =21.52 PI =10.76
S.NO AMINO ACID THREE LETTER CODE ONE LETTER CODE PK1 PK2 PK3 PI 1 ALANINE Ala A 2.34 9.69 6.01 2 VALINE Val V 2.32 9.62 5.97 3 LEUCINE Leu L 2.36 9.60 5.98 4 ISOLEUCIN Ile I 2.36 9.68 6.02 5 PROLINE Pro P 1.99 10.96 6.48 6 PHENYLALNINE Phe F 1.83 9.13 5.48 7 TRYPTOPHAN Trp W 2.38 9.39 5.89 8 METHIONINE Met M 2.28 9.21 5.74 9 GLYCINE Gly G 2.34 9.60 5.97 10 SERINE Ser S 2.21 9.15 13.60 5.68
S.NO AMINO ACID THREE LETTER CODE ONE LETTER CODE PK1 PK2 PK3 PI 11 THERONINE Thr T 2.11 9.62 13.60 5.87 12 TYROSINE Tyr Y 2.20 9.11 10.07 5.66 13 CYSTEINE Cys C 1.96 8.18 10.28 5.07 14 ASPARGININE Asp R 2.02 8.80 5.41 15 GLUTAMINE Gln Q 2.17 9.13 5.65 16 ASPARTETE Asd D 1.88 9.60 3.65 2.77 17 GLUTAMATE Glu E 2.19 9.67 4.25 3.22 18 LYSINE Lys K 2.18 8.95 10.53 9.74 19 ARGININE Arg R 2.17 9.04 12.48 10.76 20 HISTIDINE His H 1.82 9.17 6.00 7.59
BIOLOGICAL PROPERTIES: Alanine (A/Ala). Important source of energy for muscle. One of the three most important glycogenic amino acids. The primary amino acid in sugar metabolism. Boosts immune system by producing antibodies. Valine (V/Val): Essential for muscle development.
Leucine(L/Leu) Beneficial for skin, bone and tissue wound healing. Isoleucine (I/Ile). Necessary for the synthesis of hemoglobin. Phenylalanine (F/Phe). Beneficial for healthy nervous system. It boosts memory and learning. Threonine (T/Thr). Required for formation of collagen. Helps prevent fatty deposits in liver. Aids in antibodies' production.
Lysine (L/Lys). Component of muscle protein, and is needed in the synthesis of enzymes and hormones. which is essential for healthy nervous system function. Aspartate (D/Asp). Increases stamina and helps protect the liver; DNA and RNA metabolism; immune system function. Glutamate (E/Glu). Neurotransmitter that is involved in DNA synthesis.
Amino acid structure classification and properties