Anaerobic and Aerobic Glycolysis

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Anaerobic and Aerobic Glycolysis
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Topics that will be covered
Overview of Glycolysis and description of the
pathway Divergence to anaerobic metabolism
within the muscle and how does aerobic metabolism
also help energize our muscles? The three main
energy sources for our muscles.
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Glycolysis
Ancient metabolic pathway used by the earliest
bacteria This pathway existed about 1 million
years before oxygen existed on the earths
surface. Basically, glycolysis is a set of
chemical reactions that produce energy (in the
form of ATP) from the sugar glucose. In the 10
steps of glycolysis glucose is converted to
pyruvate and the reaction yeilds 2 pyruvate
molecules and 2 net ATP molecules per glucose.

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The glycolysis pathway
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Now what can be done with pyruvate?
Glycolysis produces reduced forms of NAD in the
energy generation phase. In an anaerobic
environment, lactate dehydrogenase converts
pyruvate to L-lactate and restores NADH to NAD
which can then be used in once again in the
glycolysis pathway.
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The fate of pyruvate
Pyruvate NAD CoA         Acetyl CoA CO2
NADH H
Using pyruvate in this way (to keep glycolysis
running at a paltry 2ATP per glucose) may seem
wasteful considering the much larger amount of
ATP generated should it enter the citric acid
cycle (as acetyl CoA). However, glycolysis can
run at a very high rate and thus meet the ATP
demands of the cell (at least for a short time)
even though it is a very expensive use of
glucose. But a continuous buildup of lactic
acid could lead to acidosis
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So then what do our muscles do with the lactate
produced?
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It turns out breakdown of glucose to pyruvate
within muscle cells is not the primary source of
ATP synthesis.

• ATP is the immediate source of energy for muscle
  contraction. Although a muscle fiber contains
  only enough ATP to power a few twitches, its ATP
  "pool" is replenished as needed. There are three
  sources of high-energy phosphate to keep the ATP
  pool filled.
• creatine phosphate
• glycogen
• cellular respiration in the mitochondria of the
  fibers.

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Creatine phosphate and cellular respiration as a
source of ATP for the muscle
The phosphate group in creatine phosphate is
attached by a "high-energy" bond like that in
ATP. Creatine phosphate ADP ? creatine ATP
Aerobic production of ATP aids in the
reproduction of glycogen from the lactic acid
that has built up within the muscle.
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References

• Biochemistry second edition written by
  Christopher Mathews and
• K.E. Van Holde.
• Pictures from
• http//users.rcn.com/jkimball.ma.ultranet/BiologyP
  ages/M/Muscles.html
• http//www.umanitoba.ca/faculties/medicine/units/b
  iochem/coursenotes/blanchaer_
• tutorials/Bob/metabolism
• http//www.arabidopsis.org1555/ARA/new-image?type
  PATHWAYobject
• ANAGLYCOLYSIS-PWY