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Cellular Respiration without Oxygen. The mitochondria require oxygen as the final electron acceptor of the ETC What if there isn’t ENOUGH oxygen? How will NAD + be recycled in glycolysis?. Fermentation.
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Cellular Respiration without Oxygen • The mitochondria require oxygen as the final electron acceptor of the ETC • What if there isn’t ENOUGH oxygen? How will NAD+ be recycled in glycolysis?
Fermentation • organisms have developed a way to oxidize NADH back into NAD+ without requiring oxygen • allows glycolysis to continue to produce 2 ATP. • One such process, called FERMENTATION, happens when NADH transfers H+ ions to items not in the ETC • In eukaryotes, this can be either: • ETHANOL FERMENTATION • LACTIC ACID FERMENTATION
Ethanol Fermentation • Pyruvate is broken down into carbon dioxide and acetaldehyde. • NADH transfers its hydrogen atoms to acetaldehyde to form ethanol. • NAD+ is recycled and glycolysis continues. • Yeast cells perform ethanol fermentation and can be used to make wine, beer, etc.
Lactic Acid Fermentation • Begins during strenuous exercise when muscle cells use glucose faster than oxygen is supplied. • NADH transfers its hydrogen atoms to pyruvate to form lactic acid and to regenerate NAD+. • Accumulation of lactic acid in muscle cells causes stiffness, soreness and fatigue. • When exercise stops, lactic acid converts back to pyruvate and aerobic respiration continues.