Nature's tools Proteins and Enzymes

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  • Created by: jessica
  • Created on: 10-12-12 18:42
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  • Nature's tools Proteins and Enzymes
    • Amino Acids
      • Are chiral have 2 mirror image forms-D and L
        • Only L isomers used to make proteins
      • Are zwitterions
      • 20 different amino acids
        • R groups make them different
          • Side groups with just C-H are non polar and hydrophobic
          • Side groups with N-H are polar and hydrophilic
      • form peptide bonds by carboxyl group of one amino acid joining to amino group of another
    • Protein Structure
      • Amino acids joining together forming polypeptide chains
        • Sequence of amino acids determines structure
      • mass measured in daltons
      • most proteins are trans configuration
      • Primary, Secondary, Tertiary and Quarternary Structure
        • tertiary
          • Reverse turns turns, Beta turns, hairpin  turns, omega loops further fold the structure
        • Secondary is when alpha helix, Beta sheets and strands form by folding of the polypeptide chain  and held in place by hydrogen  bonding
          • Right handed helices are energetically more favourable
          • Beta Sheets can be parallel or antiparallel
        • Quarternary
          • is the spatial arrangement of subunits and the nature of their interactions
        • Primary is the initial sequence
    • Enzymes
      • Biological catalysts
      • Competitive non competitve and uncompetitve inhibitors
        • uncompetitive binds to enzyme substrate complex effecting both Vmax and KM
        • Competitive similar to substrate shape, doesnt affect Vmax but increases Km
        • Non competitive binds to different binding site preventing enzymesubstrate complex forming, decreases Vmax, Km stays the same
      • Arrhenius equation K=A-exp-Ea/RT
      • Rate constants changes Km and Vmax values
      • decrease deltaG (activation energy)
      • Active sites are 3D clefts/crevices that create microenvironments
      • Km/Kcat is a measure of catalytic efficiency
      • Activity regulated by allosteric control,multiple forms of enzyme,reversible covalent modification, proteolytic activation, controlling amount of enzyme present
    • Protein determination and purification techniques
      • Purification methods
        • Salting out, Dialysis, Gel-filtration chromatography, ion exchange chromatography, High pressure liquid chromatography
          • Salting out-fractionates proteins due to different solubilities
          • Dialysis-separates proteins and small molecules through semi permeable membrane in a buffer solution
          • Gel filtration Chromatography-sample applied to top of column with porous beads small and large molecules take different routes through the column
          • Ion exchange chromatography-proteins separated on basis of their net charge
          • High pressure liquid chromatography is an enhanced version of column technique
        • Purification level is the measure of increase in purity and obtained by dividing specific activity
      • 3D structure determined by X ray crystallography and NMR Spectroscopy
        • X ray crystallography gives atomic detail
        • NMR Spectroscopy shows structures of proteins in solution
    • Lipids and Cell Membranes
      • lipids serve as fuel molecules, energy stores, signal molecules messengers in in signal transduction pathways, components of membranes
      • fatty acids are key components of lipids
      • 3 main types are glycolipids, phosholipids, cholesterol
      • lipids are water insoluble biomolecules that are highly soluble in organic solvents
      • membrane lipids have both hydrophobic and hydrophilic moiety
    • Fatty Acid Metabolism
      • Fatty acids oxidised in peroxisomes
      • Degradation is an oxidative process
      • Epinephrine and glucagon induce lipolysis
      • Fatty acids stored as triglycerides
      • fatty acids synthase used to synthesize fatty acids in the cytoplasm


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