Chapter 9 Cellular Respiration and Fermentation

Lactic acid fermentation is a process in which

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Lactic acid fermentation is a process in which pyruvate produced by glycolysis begins to accept electrons from NADH and fermentation takes place. Lactic acid fermentation forms a product called lactate and regenerates NAD + . o Lactic acid fermentation occurs in humans o Alcohol fermentation occurs in yeast Fermentation is extremely inefficient compared to aerobic cellular respiration.
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It is an alternative mode of energy production for typically aerobic organisms when oxygen supplies temporarily run out. Organisms that can switch between fermentation and cellular respiration that uses oxygen as an electron acceptor are called facultative aerobes. Cells have two fundamental requirements: 1. Energy 2. Carbon Reactions that break down molecules and produce ATP are called catabolic pathways. Reactions that synthesize larger molecules from smaller components are called anabolic pathways. Catabolic Pathways Break Down Molecules as Fuel Carbohydrates are not the only important source of carbon compounds used in catabolic pathways. Fats are highly reduced macromolecules consisting of glycerol bonded to chains of fatty acids. Essentially, enzymes break down fats to form glycerol and acetyl CoA. Acetyl CoA enters the citric acid cycle while glycerol is oxidized and phosphorylated. Proteins can also be catabolized, meaning that they can be broken down and used to produce ATP. When all three types of molecules are available in the cell to generate ATP, carbohydrates are used up first, then fats, then proteins. Anabolic Pathways Synthesize Key Molecules Intermediates in carbohydrate metabolism: o In humans, ~half of the 21 required amino acids can be synthesized from molecules siphoned from the citric acid cycle. o Acetyl CoA is the starting point for anabolic pathways that result in the synthesis of fatty acids. o If ATP is abundant, pyruvate and lactate can be used as a substrate in the synthesis of glucose. Excess glucose is converted to glycogen and stored. Catabolic and Anabolic pathways are closely intertwined. An Overview of Cellular Respiration Glycolysis: Processing Glucose to Pyruvate Processing Pyruvate to Acetyl CoA The Citric Acid Cycle: Oxidizing Acetyl CoA to CO 2 Electron Transport and Chemiosmosis: Building a Proton Gradient to Produce ATP
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Fermentation How Does Cellular Respiration Interact with Other Metabolic Pathways?
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