B4 - Microbes

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  • Created by: Naomi
  • Created on: 20-01-13 21:38
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  • Microbes
    • Bacteria
      • Bacteria have certain features that allow them to survive, these include:
        • A cell wall to maintain shape and stop it from bursting
        • A flagella for movement
        • DNA to control the cells activities and replication of the cell
      • 3 different shapes:
        • Bacilla (rod shape)
        • Cocci (spherical)
        • Spirilla (spiral)
      • Reproduce asexually by splitting into 2. They clone themselves
        • Called binary fission
      • Bacteria are very successful in terms of numbers because:
        • They can survive on an enormous range of different energy sources
        • They can live in a wide range of habitats
        • Some live by taking in organic nutrients, others can make their own food
      • Reproduce very quickly
    • Viruses
      • Not living cells, but made up of a protein coat surrounding a strand of genetic material
      • They can only reproduce in other living cells
        • 1. They attach themselves to a host cell
          • 2. Inject its genetic material into the cell
            • 3. Use the cell to make components of the new virus
              • 4. Cause the host cell to split open and die to release the virus
    • Yeast
      • Yeast is a single celled fungus that is grown for many functions
      • Its growth rate can be altered by:
        • Changing temperature
          • The growth rate doubles for every 10 degree rise in temperature until the optimum
        • Changing pH
        • Changing food availability
        • Removing waste products
      • Fermentation
        • The process of fermentation in yeast involves anaerobic respiration
          • glucose ---> ethanol+carbon dioxide
          • When yeast is used in brweing it soon uses up all the oxygen in the container by respiring aerobically. This allows the number of cells to increase rapidly
            • The conditions are kept anaerobic so that alcohol is made
        • The process of patturisation is brweing ot kill harmful microbes. The liquid is kept at an elevated temperature for a predetermined time
        • The alcohol concentration produced by brewing is limited . This is because high concentrations of alcohol kills yeast cells
    • Yoghurt making
      • 1. All the equipment is stepilised using aseptic techniques
        • 2, The milk is pasteurised by heating it to 78 degrees
          • 3. The milk is cooled down and is incubated with a culture of bacteria
            • The milk has to be cooled so that the bacteria isn't killed when it is added
            • The bacteria that is added is called lactobacillus
              • It causes the breakdown of lactose in milk into lactic acid, which makes the yoghurt taste acidic
    • Disease transmission
      • Disease causing microorganisms can be passed on in a number of different ways
        • Some microbes, such as salmonella, are spread in food
          • They can be prevented from spreading by correct food hygiene
        • Some, such as cholera, may be spread in water
          • They can be prevented by correct water treatment
        • Other microbes need direct contact
          • They can be prevented from spreading by barrier methods
        • Many microbes, such as those that cause flu are spread in airbourne droplets
          • They can be stopped from spreading by correct use of tissues and isolation of patients
      • There are four stages in an infectious disease
        • 1. The microbe enters the body
          • 2. It reproduces many times without causing symptoms. This is called the incubation period
            • 3. The microbes cause the production of many toxins
              • 4. These toxins cause symptoms
    • Treatment of disease
      • Many scientists have made important discoveries that have helped prevent microbes from causing disease
        • Louis Pasteur
          • Helped prove germ theory of disease by realising that microbes from the air could make food go bad
        • Joseph Lister
          • Invented the first antiseptic
            • Antiseptics are used outside of the body to kill microbes and prevent their entry
              • Work on most microbes
        • Sir Alexander Fleming
          • Discovered the first antibiotic penicillin, which is made from a fungus
            • Antibiotics are used inside the body to kill microbes
              • Have no affect on viruses
      • Problems are occuring because some bacteria are developing resistance to antibiotics
        • This resistance appears in bacterium by a mutation
          • Because bacteria can the survive and reproduce the resistance is spread by natural selection
            • To try and prevent spreading, docator take various steps
              • They only prescribe antibiotics when really necessary
              • They advise patients to finish the dose so partially resistant bacteria are killed

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