Related Pathways of Cellular Respiration by dffhrtcv3


									Related Pathways of
Cellular Respiration
 Not the hard part. In fact, if you
know the normal path, this should
            be easy.
                 Alternate Fuels
   Carbs are the first choice. What if we don’t eat carbs?

 Proteins are the third choice of energy – after carbs and
 Amino acids undergo deamination in which the amino
  groups (-NH2) are removed and made into ammonia.
 The remainder of the amino acid is converted into an
  intermediary of glycolysis or the Kreb’s cycle depending
  on the identity (R-group) of the amino acid.
                        Fat Fuel
   Lipids are the second choice for the body (despite the
    fact they hold more energy per unit than any carb).
   Triglycerides are the main fat in food – they are broken
    down into fatty acids and glycerol.
   Glycerol may go through gluconeogenesis and be
    converted into glucose or enter glycolysis as one of the
    3-carbon intermediaries.
   Fatty acids undergo ß-oxidation in which they are cut
    into 2-carbon pieces that enter the Kreb’s cycle as
    Acteyl-CoA’s. (Do the math – its huge!)
         Anaerobic Pathways
 The term “anaerobic” means “in the absence of
 There are many methods of anaerobic
  respiration but eukaryotes mostly use just two
  methods of anaerobic respiration – ethanol
  fermentation and lactate (lactic acid)
  fermentation. Fermentation means the process
  is anaerobic.
 Both processes will use glycolysis to start as it
  does not require oxygen. The difference will be
  what we do with the pyruvate at the end of
               Why Ferment?
 Glycolysis occurs first and gives a small yield of
  ATP but in the process you use up some NAD+.
  Without the ETC being used because it is
  aerobic, the NADH’s stay as NADH’s and all of
  the NAD+ gets used up and you can't even run
  glycolysis after a while.
 You have to have a way to recycle your NAD+
  and NADH or you won’t even be able to get the
  little bit of energy glycolysis offers. That is why
  things run fermentation.
 It’s not a lot of energy but it is way better than
  no energy!
             Ethanol Fermentation
    Ethanol fermentation is an anaerobic respiration process
     carried out by yeast cells – they can run fermentation and
     survive just fine because yeast cells do not require a lot of
     energy – they are boring!
    So here is what happens…
    1.   Glycolysis: Glucose  2 Pyruvate
    2.   2 Pyruvate  2 Acetaldehyde + 2 CO2
    3.   2 Acetaldehyde  2 Ethanol
    During this, we get the recycling of NAD+ and NADH.

    Ethanol fermentation is used in bread, beer and wine
Ethanol Fermentation
        Lactate Fermentation
 Lactate fermentation occurs in animals like us
  humans when we exert high physical demands
  on our body
 Our cell’s energy needs exceed our body’s ability
  to supply oxygen – we can’t breathe fast enough
  so the cells have to use something other than
 We use lactate fermentation but can’t do so for
  long because glycolysis does not give enough
  ATP to keep us going. We need a lot of ATP!
    Lactate/Lactic Acid Fermentation
    So what do we do when we can’t breathe fast
    1.   Glycolysis: Glucose  2 Pyruvate
    2.   2 Pyruvate 2 Lactate
    The NAD+ and NADH are recycled during this process.

    After the strenuous activity – we still breath hard to
     repay the oxygen debt. The oxygen goes back in to
     catabolize the lactate to CO2 and H2O.
    We use lactic acid fermentation when we want to build
     muscle – feel the burn!
Lactate/Lactic Acid Fermentation
(Yeah, you may have worked hard, but
   not hard enough to feel the burn.)

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