Country: United States
Date: February 2005
Why does glycolysis still exist when the earth is aerobic?
Are you confusing glycolysis and fermentation? Glycolysis is just the first
step in cellular respiration and fermentation and doesn't require the
presence of oxygen. In order for an organism to continue the complete combustion of
a molecule of glucose, THEN oxygen must be present. It is obviously a much
more efficient system and organisms that could gather all the raw materials
together to put this system together had a definite survival advantage. But
when no oxygen is available or oxygen can't be replaced as fast as it is used,
fermentation allows SOME energy to be produced. And that is better than
nothing. Just because a more efficient system develops over time, that doesn't
mean the old one necessarily is discarded by natural selection. And by the
way, not all of the earth is aerobic.
Even though the earth is overall aerobic, there are micro-environments that
have low concentrations of Oxygen. Examples are certain environments where
bacteria and yeast are growing and your own tissues when you are exercising
strenuously. Your own cells carry-out glycolysis to produce ATP and lactic
acid when your heart and lungs can't keep up with the Oxygen demand of your
muscles during strenuous activity.
Ron Baker, Ph.D.
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Update: June 2012