protein

• monomer unit of protein


  amino acid
• protein is the second most abundant with 15% of cell mass
• protein contains c, h, n, o, s, fe, p
• nitrogen in protein contains 15.4% of mass
• amino acid


  organic compound
• amino acid contains


  amino (-NH2) and carboxyl (-COOH) which is attached to the same alpha carbon
• standard amino acid is divided into 4
• non polar amino acid 


  hydrophobic
• 8 out of 20 standard amino acid are non polar
• polar amino acid

  hydropholic

  • polar neutral
  • polar acidic : COOH
  • polar basic : NH2
• nomenclature

  • three letter abbreviation
  • one letter symbol
• chiral center exhibits enantiomerism
• amino acid found in nature and protein is L isomer
• bacteria have D amino acid
• in pure form, amino acid are white crystalline solid
• amino acid decomposes before they melt
• acid-base amino acid exist as zwitterion wherein COOH is negative and NH2 is positive
• amino acid in solution

  • zwitterion
  • positive ion
  • negative ion
• isoelecelectric point

  highest amount of zwitterion with zero net charge
• crysteine is a standard AA with -SH (sulfhydryl) group
• -SH group gives crysreine a chemical property that makes it unique
• crysteine combines to form crystine molecule when it is in the presence of mild oxidizing agent
• when peptides is in a proper condition, the AA bonds together which produces an unbranced chain of AA
• peptide is a chain of covalently-linked AA
• peptide

  • dipeptide
  • oligopeptide
  • polypeptide
• every peptide has N terminal end and C terminal end
• isomeric peptide

  peptide that has the same acid but in different order are different molecule with different property
• small peptide hormone

  • produced by pituitary gland
  • nonapeptide
• small pepdite neurotransmitter

  • enkephalin : produced by the brain and bind receptor
  • reduces pain
• small peptide antioxidant

  • regulator of oxidation-reduction reaction
  • glutathion : antioxidant the protects oxidizing agents
• protein is a peptide where at least 40 AAR are present
• more than one peptide chain are present in protein

  • monomeric: one peptide chain
  • multimeric: more than one peptide chain
• classification of protein

  • simple protein
  • conjugated protein
• simple protein


  composed of only amino acid residue
• conjugated protein

  has one or more non amino acid entities present in its structure

  • lipoprotein
  • glycoprotein
  • metalloprotein
• types of structure

  • primary structure
  • secondary structure
  • tertiary structure
  • quaternary structure
• primary structure

  order wherin the aino acid in linked in a protein

  • frederick sanger - insulin
• secondary structure

  the peptide linkage lies in the same plane which allows only two possible arrangment for peptide bone
• secondary structure

  • alpha helix: single protein chain, intramolecular, coiled spring shape
  • beta pleated sheet: extended amino acid chain, intramolecular/intermolecular
• tertiary structure

  interaction of the amino acid side chain that is seperated with each other