Proteins

• R group


  • Hydrophilic
  • Polar/charged
  • Acidic
  • Basic
  • Hydrophobic
• Amino acid + amino acid

  1. Condensation

  2. Dipeptide (peptide bond)

  3. Water
• Proteins


  Made up of amino acids
• Amino acids


  • 20 different
  • Essential
  • Non-essential
• Essential amino acids


  Obtained from diet
• Non-essential amino acids


  Can be made from other amino acids/self
• Vegans need to know which amino acids are consumed
• Formation of a dipeptide

  1. Carboxyl and amine group

  2. Lose a water

  3. Peptide bond
• Proteins and the genetic code

  1. Genes on DNA code for polypeptide chains

  2. Genetic code is transcribed onto mRNA

  3. mRNA translated by ribosomes into a polypeptide chain
• Peptide chains can have any number of amino acids
• Polypeptides


  • Lysozyme
  • Alpha neurotoxins
  • Glucagon
  • Myoglobin
• Lysozyme


  Enzyme in tears and saliva, antimicrobial, disrupts cell walls
• Alpha neurotoxins


  Snake venom, target nervous system, bind to and inhibit specific receptors
• Glucagon


  Hormone that regulates blood sugar levels, liver releases stored glucose
• Myoglobin


  Oxygen binding protein, releases oxygen during low oxygen availability
• Effect on pH and temp

  Denaturation - conformational change -> protein structure is altered, losing function usually permanently
• High temps


  Vibrations break bonds
• Higher pH


  Amino acid charge changes and breaks the ionic bond
• Enzyme active site changes shape


  Cannot bind to substrates
• Some organisms have proteins that only function at higher temperatures
• Primary structure


  Chain of amino acids, determined by nucleotide base sequence of a gene, joined together by peptide bonds through condensation
• Secondary structure


  Local folding into helixes/sheets, Alpha helixes, Beta pleated sheets, Hydrogen bonds between C=O and N-H
• Tertiary structure


  3D folding pattern due to side chain interactions, Ionic bonds between charged R groups, Covalent bonds, Disulfide bonds, Disulfide bridges between two cysteine amino acids, Hydrogen bonding, Hydrophilic + hydrophobic interactions, Can be globular (ball) or fibrous (rope)
• Quaternary structure


  More than one amino acid chain, Held together due to R groups, Hydrogen bonds, Covalent bonds, Disulfide bridges, Ionic bonds, Hydrophobic + phillic interactions, Globular/fibrous, Imbedded part of the integral membrane proteins contains hydrophobic R groups
• Conjugated proteins


  Protein attached to a prosthetic (non-polypeptide) group, Adult hemoglobin is a globular conjugated protein
• Insulin


  Non-conjugated - only polypeptides, Globular, 2 polypeptide chains, Linked by 2 disulfide bridges, Regulates blood glucose levels
• Collagen


  Non conjugated, Fibrous, 3 tightly coiled polypeptide chains, Strength, support, elasticity, Structural protein found in connective tissue
• Cryogenic electron microscope can see single protein molecules + interactions, Understand protein structure + functions
• Similarities between insulin and collagen

  Composed of amino acids joined by peptide bonds during translation, Quaternary structure with more than one polypeptide
• Differences between insulin and collagen

  Insulin is globular, collagen is fibrous, Insulin is spherical, collagen is long and narrow, Insulin has irregular amino acids + hydrophobic core, Insulin is water soluble, has two polypeptides and disulfide bonds