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Structure and function of amino acid and proteins, Amino_Acid_Structure -…
Structure and function of amino acid and proteins
General Structure of an Amino acid
Amino acids are the smallest units of a protein
The molecular structure of amino acids consists of an amino group (NH2), a carboxyl group (COOH), and an -R (side) group. chain)
Classification of Amino Acids
Aromatic amino acids
Phenylalanine, Tyrosine
Heterocyclic amino acids
Tryptophan, Histidine
Aliphatic amino acids
•
Simple amino acids:
Glycine, nine
• Branched chain amino acids:
Valine, Leucine, Isoleucine
• Hydroxy amino acids:
Serine, Threonine
• Sulphur containing amino acids:
Cysteine, Methionine
•
Amino acids with amide group:
Asparagine, Glutamine
Imino acid
Proline
Chemical and Physical Properties of Amino Acids
Acid-Base and Buffer Properties of Amino Acids
7.4, both carboxyl and amino groups of amino acids are completely ionized
Isoelectric point or pI
Solubility and buffering capacity will be minimum
Optical Activity
The L-amino acids occur in nature Natural amino acids
Peptide Bond Formation
Covalently join the a-carboxyl group (-COOH) of each amino acid to the a-amino group (-NH2)
rotate freely
N rotated with angle (phi)
C rotated with angle (psi)
Protein Structure
Secondary structure
Regular arrangements in space of adjacent amino acid residues in a polypeptide chain
Tertiary structure
among all amino acids in a polypeptide
Quaternary structure
The overall spatial arrangement of poly peptides
Primary structure
polypeptides linking with peptide bond
Classification
of Protein
Solubility properties
Soluble in water: Albumins, Protamines
Insoluble in water: Globulins, Prolamines
Chemical composition
Conjugated proteins
Simple proteins
Protein configuration
Fibrous proteins
Globular proteins
