Metabolism without Oxygen Quiz

PDF page 310: As was previously stated, under aerobic conditions cellular respiration can yield 36-38 ATP molecules. If oxygen is not present, ATP is only produced by substrate-level phosphorylation. Without oxygen, organisms must use another electron

PDF page 310: As was previously stated, under aerobic conditions cellular respiration can yield 36-38 ATP molecules. If oxygen is not present, ATP is only produced by substrate-level phosphorylation. Without oxygen, organisms must use another electron

PDF page 310: acceptor. Most organisms will use some form of fermentation to accomplish the regeneration of NAD to ensure the continuation of glycolysis. In alcohol fermentation, pyruvate from glycolysis is converted to ethyl alcohol; during lactic acid fermentation, pyruvate is reduced to form lactate as an end-product. Without fermentation and anaerobic respiration, we wouldn’t have yogurt or soy sauce. Nor would our muscle cells cramp from the buildup of lactate when we exercise vigorously and oxygen is scarce. Information presented and the examples highlighted in the section support concepts and Learning Objectives outlined

PDF page 310: acceptor. Most organisms will use some form of fermentation to accomplish the regeneration of NAD to ensure the continuation of glycolysis. In alcohol fermentation, pyruvate from glycolysis is converted to ethyl alcohol; during lactic acid fermentation, pyruvate is reduced to form lactate as an end-product. Without fermentation and anaerobic respiration, we wouldn’t have yogurt or soy sauce. Nor would our muscle cells cramp from the buildup of lactate when we exercise vigorously and oxygen is scarce. Information presented and the examples highlighted in the section support concepts and Learning Objectives outlined

PDF page 311: The Science Practice Challenge Questions contain additional test questions for this section that will help you prepare for the AP exam. These questions address the following standards: [APLO 2.21][APLO 2.24][APLO 4.14][APLO 4.26] In aerobic respiration, the final electron acceptor is an oxygen molecule, O2. If aerobic respiration occurs, then ATP will be produced using the energy of high-energy electrons carried by NADH or FADH2 to the electron transport chain. If aerobic

PDF page 311: an organic molecule to regenerate NAD from NADH are collectively referred to as fermentation. In contrast, some living systems use an inorganic molecule as a final electron acceptor. Both methods are called anaerobic cellular respiration in which organisms convert energy for their use in the absence of oxygen.

PDF page 311: an organic molecule to regenerate NAD from NADH are collectively referred to as fermentation. In contrast, some living systems use an inorganic molecule as a final electron acceptor. Both methods are called anaerobic cellular respiration in which organisms convert energy for their use in the absence of oxygen.

PDF page 311: Certain prokaryotes, including some species of bacteria and Archaea, use anaerobic respiration. For example, the group of Archaea called methanogens reduces carbon dioxide to methane to oxidize NADH. These microorganisms are found in soil and in the digestive tracts of ruminants, such as cows and sheep. Similarly, sulfate-reducing bacteria and Archaea, most of

PDF page 311: which are anaerobic ( Figure 7.14), reduce sulfate to hydrogen sulfide to regenerate NAD from NADH.

PDF page 312: Lactic Acid Fermentation The fermentation method used by animals and certain bacteria, like those in yogurt, is lactic acid fermentation (Figure 7.15). This type of fermentation is used routinely in mammalian red blood cells and in skeletal muscle that has an insufficient oxygen supply to allow aerobic respiration to continue (that is, in muscles used to the point of fatigue). In muscles, lactic acid accumulation must be removed by the blood circulation and the lactate brought to the liver for further metabolism. The chemical reactions of lactic acid fermentation are the following:

PDF page 312: Lactic Acid Fermentation The fermentation method used by animals and certain bacteria, like those in yogurt, is lactic acid fermentation (Figure 7.15). This type of fermentation is used routinely in mammalian red blood cells and in skeletal muscle that has an insufficient oxygen supply to allow aerobic respiration to continue (that is, in muscles used to the point of fatigue). In muscles, lactic acid accumulation must be removed by the blood circulation and the lactate brought to the liver for further metabolism. The chemical reactions of lactic acid fermentation are the following:

PDF page 313: Pyruvic acid + NADH ↔ lactic acid + NAD The enzyme used in this reaction is lactate dehydrogenase (LDH). The reaction can proceed in either direction, but the reaction from left to right is inhibited by acidic conditions. Such lactic acid accumulation was once believed to cause muscle stiffness, fatigue, and soreness, although more recent research disputes this hypothesis. Once the lactic acid has been removed from the muscle and circulated to the liver, it can be reconverted into pyruvic acid and further catabolized for energy.