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Name: Kirt
Status: Student
Grade:  9-12
Location: NY
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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