6.13 Fermentation. Fermentation is an anaerobic (without oxygen) energy-generating process It takes advantage of glycolysis, producing two ATP molecules and reducing NAD + to NADH The trick is to oxidize the NADH without passing its electrons through the electron transport chain to oxygen.
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6.13 Fermentation • Fermentation is an anaerobic (without oxygen) energy-generating process • It takes advantage of glycolysis, producing two ATP molecules and reducing NAD+ to NADH • The trick is to oxidize the NADH without passing its electrons through the electron transport chain to oxygen
6.13 Fermentation • Most cellular respiration requires O2 to produce ATP • Glycolysis can produce ATP with or without O2 (in aerobic or anaerobic conditions) • In the absence of O2, glycolysis couples with fermentation or anaerobic respiration to produce ATP
6.13 Lactic Acid Fermentation • Your muscle cells and certain bacteria can oxidize NADH through lactic acid fermentation • NADH is oxidized to NAD+ when pyruvate is reduced to lactate • Pyruvate is serving as a place to dispose of the electrons generated in glycolysis • Products: 2 NAD+, lactic acid, 2ATP(from glycolysis) • Can be added to milk to make cheese…..how?
Glucose 2 NAD+ 2 ADP 2 P GLYCOLYSIS 2 ATP NADH 2 2 Pyruvate NADH 2 2 NAD+ 2 Lactate Lactic acid fermentation
6.13 Fermentation enables cells to produce ATP without oxygen • The baking and wine-making industry have used alcohol fermentation for thousands of years • Yeasts are single-celled fungi that not only can use respiration for energy but can ferment under anaerobic conditions • They convert pyruvate to CO2 and ethanol while oxidizing NADH back to NAD+ • Products: ethyl alcohol, 2CO2 , 2 NAD+, 2ATP • Can be added to grapes to make wine….how?
Glucose 2 NAD+ 2 ADP P 2 GLYCOLYSIS 2 ATP NADH 2 2 Pyruvate NADH 2 CO2 2 released 2 NAD+ 2 Ethanol Alcohol fermentation
Obligate anaerobes carry out fermentation or anaerobic respiration and cannot survive in the presence of O2 • Yeast and many bacteria are facultative anaerobes, meaning that they can survive using either fermentation or cellular respiration
Fig. 9-19 Glucose Glycolysis CYTOSOL Pyruvate O2 present: Aerobic cellular respiration No O2 present: Fermentation MITOCHONDRION Acetyl CoA Ethanol or lactate Citric acid cycle
Regulation of Cellular Respiration via Feedback Mechanisms • Feedback inhibition is the most common mechanism for control • If ATP concentration begins to drop, respiration speeds up; when there is plenty of ATP, respiration slows down • Control of catabolism is based mainly on regulating the activity of enzymes at strategic points in the catabolic pathway
You should now be able to: • Explain in general terms how redox reactions are involved in energy exchanges • Name the three stages of cellular respiration; for each, state the region of the eukaryotic cell where it occurs and the products that result • In general terms, explain the role of the electron transport chain in cellular respiration
Explain where and how the respiratory electron transport chain creates a proton gradient • Distinguish between fermentation and anaerobic respiration • Distinguish between obligate and facultative anaerobes