PROTEIN NG MAMA MO

• Protein


  A naturally-occurring, unbranched polymer in which the monomer units are amino acids

  
• Proteins are the most abundant molecules in cells after water - account for about 15% of a cell's overall mass
• Amino acid


  An organic compound that contains both an amino (-NH2) and carboxyl (-COOH) groups attached to same carbon atom

  
• Elements found in proteins

  • Carbon (C)
  • Hydrogen (H)
  • Nitrogen (N)
  • Oxygen (O)
  • Sulfur (S)
  • Iron (Fe)
  • Phosphorus (P)
  • Other metals
• The average nitrogen content of proteins is 15.4% by mass
• Standard amino acids


  • Non-polar
  • Polar neutral
  • Polar acidic
  • Polar basic
• Non-polar amino acids


  Hydrophobic (water-fearing, insoluble in water)
• Polar neutral amino acids


  Contain polar but neutral side chains
• Polar acidic amino acids


  Contain carboxyl group as part of the side chains

  
• Polar basic amino acids


  Contain amino group as part of the side chain

  
• Amino acid nomenclature


  Common names, three letter abbreviations, one letter symbols
• Chirality


  19 of the 20 standard amino acids contain a chiral center and exist in left and right handed forms (L and D isomers)

  
• The amino acids found in nature as well as in proteins are L isomers

  
• Zwitterion


  An ion with + (positive) and - (negative) charges on the same molecule with a net zero charge
• Isoelectric point (pI)


  pH at which the concentration of Zwitterion is maximum - net charge is zero
• Cysteine


  The only standard amino acid with a sulfhydryl group (-SH)
• Cystine


  Two cysteine residues linked via a covalent disulfide bond

  
• Peptide


  An unbranched chain of covalently-linked amino acids

  
• Types of peptides


  • Dipeptide
  • Oligopeptide
  • Polypeptide
• Peptide nomenclature


  1. terminal amino acid keeps full name, other amino acids have -yl suffix

  
• Isomeric peptides


  Peptides with same amino acids but in different order are different molecules

  
• Biochemically important small peptides


  • Hormones
  • Neurotransmitters
  • Antioxidants
• Oxytocin and vasopressin


  Small peptide hormones produced by the pituitary gland
• Enkephalins


  Small peptide neurotransmitters that help reduce pain
• Glutathione


  A tripeptide antioxidant that protects cells from oxidizing agents
• Protein


  A peptide in which at least 40 amino acid residues are present

  
• Protein classification by chemical composition


  • Simple proteins
  • Conjugated proteins
• Primary structure of proteins


  The order in which amino acids are linked together

  
• Frederick Sanger sequenced and determined the primary structure for the first protein - Insulin
• Proteins of the same organism always have the same amino acid sequence
• Insulin from different sources (pigs, cows, sheep, humans) are similar but have some differences
• Human insulin is now produced from genetically engineered organisms
• Primary Structure


  The order in which amino acids are linked together in a protein

  
• Every protein has its own unique amino acid sequence
• Frederick Sanger (1953)


  Sequenced and determined the primary structure for the first protein - Insulin
• Proteins of the same organism always have the same sequence (cows, pigs, etc.)
• Different sources: Insulin from pigs, cows, sheep, humans are similar
• Some differences in insulin may show some reaction over time
• Now human insulin is produced from genetically engineered bacteria
• Secondary Structure


  Arrangement of atoms of backbone in space