Existing in the presence of oxygen. The anaerobic catabolism of organic nutrients. Glycolysis oxidizes glucose to two pyruvic acid molecules. Glycolysis produces a net of 2 ATPs whether conditions are aerobic or anaerobic. No additional ATP is produced.
Pyruvic acid loses carbon dioxide and is converted to the two- carbon compound acetaldehyde.
Many bacteria and yeast carry out alcohol fermentation under anaerobic conditions. Commercially important products of lactic acid fermentation include cheese, yogurt, acetone and methyl alcohol. When oxygen is scarce, human muscle cells switch from aerobic respiration to lactic acid fermentation. Lactic acid accumulates, but it is gradually carried to the liver where it is converted back to pyruvic acid when oxygen becomes available. There are three major catabolic processes for harvesting food's chemical energy aerobic respiration anaerobic respiration fermentation.