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ANAEROBIC CELLULAR RESPIRATION: FERMENTATION. RECALL:. Cellular Respiration : the process of using glucose to make energy (ATP) for the cell. Aerobic Cellular Respiration (Requires Oxygen), 2 steps. On average 30 ATP. Glycolysis. Oxidative Respiration. Location. Mitochondria.
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RECALL: • Cellular Respiration: the process of using glucose to make energy (ATP) for the cell. • Aerobic Cellular Respiration (Requires Oxygen), 2 steps On average 30 ATP Glycolysis Oxidative Respiration Location Mitochondria Cytosol Reactant(s) Pyruvate + Oxygen Glucose Carbon Dioxide + Water Pyruvate Products Energy 28 ATP 2 ATP
Aerobic Cellular Respiration (requires oxygen) enzymes 6O2 + C6H12O6 6CO2 + 6H2O oxygen glucose carbon dioxide water ENERGY transfer between enzymes, other molecules ADP + Pi ATP
WHAT IF THERE’S NO OXYGEN? • Some organisms can survive with little or no oxygen in their environments! • For example, microorganisms in • The bottom of a swamp • Sewage treatment plants • Pickling food jars • Contaminated canned goods • The human gut • And many more!!! Gangrene – death of tissue due to a bacterial infection or circulatory problems.
CELLULAR RESPIRATION WITHOUT OXYGEN Glucose 2 ATP Cytosol • ANAEROBIC CELLULAR RESPIRATION • “Anaerobic:” – without oxygen • FERMENTATION • One of the types of anaerobic cellular respiration • Glucose molecule undergoes glycolysis as usual • 2 Pyruvate and 2 ATP molecules are made • Pyruvate cannot undergo oxidative respiration because it requires oxygen. • The pyruvate molecule is broken down by a fermentation reaction. • Two common fermentation reactions: • Alcohol fermentation • Lactic acid fermentation 2 Pyruvate Mitochondria
1. ALCOHOL FERMENTATION • Occurs in the cytosol • Yeast – common microorganism that undergoes alcohol fermentation. • Each pyruvate is broken down into carbon dioxide and ethanol (an alcohol). + C2H6O Ethanol CO2 Carbon Dioxide C3H6O3 Pyruvate 2. LACTIC ACID FERMENTATION • Occurs in the cytosol • Can take place in human muscle cells during vigorous exercise • Each pyruvate is converted to lactic acid. + C2H6O Ethanol CO2 Carbon Dioxide C3H6O3 Pyruvate
FOOD, DRINK, AND FERMENTATION • Yeast has been used for alcohol fermentation by humans since 7000BC (for over 9000 years)! • Bread • First step is to create a “starter” which will activate yeast to start creating carbon dioxide and ethanol. • Either add baker’s yeast and flour to warm water. • Make a flour & water mixture and let it sit out. Yeast from the air will colonize the mixture. • Add other ingredients and let the dough “rise.” • Beer • Brewers mix together water and a starch source (like malted barley), add yeast, and add flavouring such as hops.