Player that your browser was unable to view. Out of many possible types of fermentation processes, the two most common types are lactic acid fermentation and alcohol fermentation . Normally our muscles do cellular respiration like the rest of our bodies, using O 2 supplied by our lungs and blood. However, under greater exertion when the oxygen supplied by the lungs and blood system can't get there fast enough to keep up with the muscles' needs, our muscles can switch over and do lactic acid fermentation.
Alcohol fermentation is done by yeast and some kinds of bacteria.
Humans have long taken advantage of this process in making bread, beer, and wine. In contrast, in the process of cellular respiration , the pyruvic acid molecules are broken down completely to CO 2 and more energy released. An analogy can be drawn between our cells and a car. A part is released, eventually each 2-carbon piece is broken apart into two molecules of CO 2 . In glycolysis and the Krebs cycle, there are a number of electrons released as glucose is broken down.