tion is central to bread baking. The carbon dioxide bubbles allow the bread to rise, and the
alcohol evaporates. In wine making, the sugars of grapes are fermented to produce the wine.
Animals and some bacteria and fungi carry outlactic acid fermentation.Lactate (lactic
acid) is a waste product of this process. Our muscles undergo lactic acid fermentation during
strenuous exercise, when oxygen cannot be delivered to the muscles quickly enough. The
buildup of lactate is what makes your muscles sore after vigorous exercise. Bacteria that
produce lactate are used to make cheese and yogurt (Figure4.14). Tooth decay is also
accelerated by lactate from the bacteria that use the sugars in your mouth. In all these
types of fermentation, the goal is the same: to recycle NAD+for glycolysis.
Figure 4.14: Products of fermentation include cheese (lactic acid fermentation) and wine
(alcoholic fermentation). ( 12 )
Lesson Summary
- Cellular respiration is the breakdown of glucose to release energy in the form of ATP.
- Glycolysis, the conversion of glucose into two 3-carbon pyruvate molecules, is the first
step of cellular respiration. - If oxygen is available, the pyruvate enters the mitochondria and goes through a series
of reactions, including the citric acid cycle, to produce more ATP. - If oxygen is not available, the pyruvate is reduced during the process of fermentation
to free up more NAD+for glycolysis, and there is no net gain of ATP.