anaerobic

• what are obligate anaerobes?


  Organisms that cannot survive in the presence of oxygen, mostly prokaryotes
• what are facultative anaerobes?

  can synthesise ATP by aerobic respiration if oxygen is present but can switch to anaerobic respiration in absence of oxygen
• obligate aerobes:

  • can only synthesise ATP in the presence of oxygen
• what is fermentation?


  where complex organic compounds are broken down into inroganic compounds without the use of oxygen/etc

  • produces much less ATP than aerobic respiration
• lactate fermentation:

  • pyruvate acts as an hydrogen acceptor taking in hydrogen from reduced NAD catalysed by lactate dehydrogenase
  • pyruvate is converted into lactate and NAD regenerated
  • lactate converted back to glucose in the liver (requires oxygen)
• why can't lactate fermentation occur indefinitely?

  • reduced quantity of ATP produced would not be enough to maintain vital processes for a long period of time
  • accumulation of lactic acid causes a fall in pH leading to protein denaturation
• Alcoholic fermentation process

  • pyruvate is first converted to ethanal catalysed by enzyme pyruvate decarboxylase
  • ethanal accepts the hydrogen atom from reduced NAD becoming ethanol
  • NAD continues as a coenzyme so glycolysis can continue
• NAD importance:

  • oxygen acts as a the final electron acceptor
  • without it reduced NAD no longer releases H+ at electron transport chain
  • this creates a backlog of reduced NAD and no more NAD being regenerated
  • without NAD = krebs, link reaction and glycolysis cannot happen
• Regeneration of ATP by creatine phosphate:

  • In the presence of ADP = phosphocreatine breaks down to release energy
  • provides energy for 6-10 seconds
  • phosphocreatine regenerated at rest
• suggest how lactate and ethanol fermentation still allow production of ATP?

  Glycolysis continues producing a net gain of 2 ATP