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Fermentation 101. Ms. Levensailor. Cellular Respiration Review. Oxidation: refers to the loss of electrons to any electron acceptor (not just oxygen). For example: Glycolysis Oxidizes glucose to 2 molecules of pyruvate. Oxidizing agent of glycolysis is NAD + (not oxygen).
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Fermentation 101 Ms. Levensailor
Cellular Respiration Review • Oxidation: refers to the loss of electrons to any electron acceptor (not just oxygen). • For example: Glycolysis • Oxidizes glucose to 2 molecules of pyruvate. • Oxidizing agent of glycolysis is NAD+ (not oxygen). • Energy made is 2 ATPs (net) by substrate phosphorylation.
Cellular Respiration Review • If oxygen is present . . . • Additional ATP is made by oxidative phosphorylation. • HOWEVER, Glycolysis generates 2 ATPs whether oxygen is present or not!
Anaerobic Catabolism • Fermentation = anaerobic catabolism of organic nutrients. • Extension of glycolysis that can generate ATP using only substrate-level phosphorylation. • Requires sufficient supply of NAD+ to accept electrons during oxidation step of glycolysis. • Without a mechanism to recycle NAD + from NADH, glycolysis would deplete the cell’s pool of NAD +.
Anaerobic Catabolism • How is NAD+ recycled in aerobic conditions? • The anaerobic alternative is to transfer electrons from NADH to pyruvate. • There are many types of fermentation, differing in the waste products formed from pyruvate. • Alcohol fermentation • Lactic Acid fermentation
Alcohol Fermentation • Pyruvate is converted to ethanol (ethyl alcohol) in 2 steps. • 1. carbon dioxide is released from pyruvate, which is converted to acetaldehyde. • 2. acetaldehyde is reduced by NADH to ethanol. • Regenerating a a supply of NAD+ • Alcohol fermentation by yeast (a fungus) is used in brewing & winemaking.
Lactic Acid Fermentation • Pyruvate is reduced directly by NADH to form lactate (no release of CO2). • Lactic acid fermentation by certain fungi and bacteria are used in the dairy industry to make: • Cheese • Yogurt • Human muscles make ATP by lactic acid fermentation. • Sugar catabolism for ATP production outpaces the muscle’s supply of oxygen from the blood.
Check for Understanding • In your composition book: • Make a Venn Diagram • Compare and contrast Fermentation & Cellular Respiration Fermentation Cellular Respiration