Growth phase

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  • Created by: Steff06
  • Created on: 08-05-16 19:19
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  • Growth curve
    • Closed culture = Growth of microorganisms in an environment where all conditions are fixed and contained. No new materials are added and no waste products or organisms are removed.
    • 4 phases: 1. Lag phase, 2: Log phase, 3:Stationary phase, 4: Death phase
    • 1. Lag phase: Organisms adjusting to environment. Cells are active but not reproducing so population remains fairly constant. Length of phase depends on growing conditions.
    • 2. Log phase: Population doubles every generation as each individual has enough space and nutrients to reproduce. Length of phase depends on how quickly organisms reproduce and take up the available nutrients and space.
    • 3. Stationary phase: Nutrient levels decrease and waste products e.g. carbon dioxide + metabolites build up. Death rate is equal to birth rate. In an open system, this would be the carrying capacity of the environment.
    • 4. Death phase: Nutrient exhaustion and increased levels of toxic waste products and metabolites lead to the death rate increasing over the reproduction rate.
    • Fermentation: Refers to the culturing of microorganisms aerobically and anaerobically in fermentation tanks. The substances generated by growth of the microorganism culture are separated and treated to produce the final useful product.
    • Products of metabolic processes: New cells and cellular components, chemicals e.g.hormones and enzymes, waste products.
    • Primary metabolites: Substances produced by an organism as part of its normal growth. Include amino acids, proteins, enzymes, nucleic acids, ethanol and lactate. Production of primary metabolites matches growth of population of organism.
    • Secondary metabolites: Substances produced by an organism that are not part of its normal growth. Antibiotic chemicals produced by a no. of microorganisms are almost all secondary metabolites. Production of them usually begins after the main growth period and so does not match the growth in population of the organism.
    • All microorganisms produce primary metabolites in order to grow.
      • Only some microorganisms produce secondary metabolites.


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