NOTEs

• amino acids

  • amine group
  • hydrogen atom
  • carboxylic acid group
  • R group- variable region, different for different amino acids
• peptide bonds

  • between amino acids
  • covalent bonds
  • condensation reaction- water is released
• primary structure

  • the sequence of amino acids bonded by peptide bonds
  • DNA of cell determines structure
  • specific to each protein
• secondary

  • a helix or B-pleated sheets form
  • different bonding eg ionic or hydrogen
  • fibrous proteins have secondary
• tertiary

  • additional bonds forming between R groups eg hydrogen, ioninc, disulphide
  • 3D structure/ folding, globular proteins
• quaternary

  • more than one polypeptide chain working together
• globular protein- structure

  • compact and spherical
  • complex tertiary and quaternary structure
  • many uses eg hormones, enzymes
• globular proteins- function

  • orientation of R group, hydrophilic R groups outside can form H+ bonds with water= soluble
  • thus easily transported around organisms and be involved in metabolic reactions
• haemoglobin(globular)

  • has quaternary structure - 4 polypeptide chains
  • held together by disulphide bonds
  • carries o2 in blood as 02 binds to haem group
  • sickle cell amenia= changes in amino acid sequence
• fibrous proteins structure

  • long strands of polypeptide chains, have cross linkages due to hydrogen bonds
  • little/no tertiary structure
  • insoluble
  • used for structural purposes
• fibrous proteins function

  • large number of hydrophobic R groups on outside meaning insoluble
  • strong and insoluble- good structural roles
  • eg keratin(hair)
• collagen(fibrous protein)

  • high tensile strength due to hydrogen and covalent bonds in structure
  • 3 polypeptides which form an alpha helix
  • found in skin, bones, tendons, tissues
• enzymes

  • biological catalysts which speed up the rate of reaction without being used up or permanently changes
  • decrease activation energy
• structure of enzymes

  • globular protein with tertiary structure
  • some have quaternary
  • all enzymes are proteins
  • either intracellular(inside cell) or extracellular(secreted by cell but catalyse reactions outside cell)
• enzymes- lowering activation energy

  • AE= amount of energy needed for reaction to occur
  • they decrease stability of bonds in the reactants= more reactive
  • or provide alternative energy pathway with lower AE
• enzyme activation

  • enzymes have unique active site where specific substances bind= enzyme substrate complex
  • denaturation= high temps or extreme PH breaks bonds and alters tertiary structure of active site
• induced fit hypothesis

  • enzyme and active site can change shape slightly as substance molecule enters
  • ensure ideal binding arrangement
  • maximise ability of enzyme to catalyse reaction