• Created by: JS007
  • Created on: 09-01-18 12:32
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  • Extremophiles
    • Heat
      • hyper-thermophiles survive at 70-110 DegC
        • Problems: Proteins denature, DNA unwinds, ATP breaks down, cell membranes become more fluid
        • Contain heat shock protein which refold denatured enzymes
        • reverse DNA gyrase helps rewind DNA
        • Hydrophobic amino acids are held at the core of proteins to increase stability
        • The cytoplasm contains salts to stop molecules denaturing
        • Cell membranes contain more saturated fatty acids to increase stability
        • Many archaea have tetraethers in their cell wall, increasing stability
      • mesophiles survive at 10-45 DegC (most microbes)
      • psychrophiles survive at 10-20 DegC
    • pH
      • Acidophiles prefer low pH 1-5
        • Problems: Proteins denature and metabolic processes stop
        • Cell membranes are less permeable to protons
        • Ion channels are smaller
        • Cell may take on more K+ or Na+ ions to reduce the gradient in protons
        • May actively pump protons out of the cell
        • Cytoplasmic buffers
      • neutrophiles prefer neutral pH 5-7
      • alkaliphiles prefer high pH 8-12
    • Salinity
      • halophiles prefer high salt concentration
        • Problem: salt disrupts osmosis and may cause the cell to burst or shrink
        • May take on more K+ instead of Na+ which has less of an affect on osmosis
        • Cytoplasmic buffers
      • non-halophiles find a high salt concentration toxic
      • halotolerant organisms are unaffected by salinity


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