5.3 Cellular Respiration Releases Energy from Organic Compounds In this section, you will distinguish among aerobic respiration, anaerobic respiration, and fermentation explain how carbohydrates are oxidized by glycolysis and the Krebs cycle to produce NADH, FADH 2, and ATP explain how chemiosmosis converts the reducing power of NADH and FADH 2 to the chemical potential of ATP explain that science and technology are developed to meet societal needs such as the production of foods and fuels investigate and integrate information on the action of metabolic toxins such as hydrogen sulfide and cyanide
5.3 Cellular Respiration Releases Energy from Organic Compounds Three metabolic pathways make up aerobic cellular respiration.
5.3 Cellular Respiration Releases Energy from Organic Compounds The first set of reactions in aerobic cellular respiration is called glycolysis. It is an anaerobic process. During glycolysis, a small amount of ATP is generated, and NAD + is reduced to NADH.
Glycolysis
5.3 Cellular Respiration Releases Energy from Organic Compounds The fate of pyruvate, the final product of glycolysis, depends on the availability of oxygen and on the type of organism. When oxygen is available, pyruvate enters the matrix of the mitochondrion. The transition reaction yields carbon dioxide and acetyl- CoA. NAD + is reduced to NADH.
5.3 Cellular Respiration Releases Energy from Organic Compounds Acetyl-CoA enters the Krebs cycle by combining with a fourcarbon compound. During the Krebs cycle: two carbon atoms are fully oxidized to carbon dioxide, NAD + and FAD are reduced to NADH and FADH 2, a small amount of ATP is produced.
Krebs (TCA or Citric Acid) Cycle
5.3 Cellular Respiration Releases Energy from Organic Compounds The NADH and FADH 2 from the Krebs cycle are important reduced compounds They donate their electrons to the electron carriers in the electron transport chain. ELECTRON TRANSPORT SYSTEM Site of chemiosmosis As electrons are passed from one carrier to the next, the energy that is released is used to pump hydrogen ions across the mitochondrial inner membrane into the intermembrane space, creating a concentration gradient The energy stored in the gradient is used to generate ATP by chemiosmosis as protons go through ATP synthase
ELECTRON TRANSPORT SYSTEM
5.3 Cellular Respiration Releases Energy from Organic Compounds Organisms that carry out fermentation use inorganic chemicals other than oxygen as the final electron-acceptor. This produces ATP for the cell, but not as much as in aerobic respiration. breakdown of glucose in the presence of oxygen breakdown of glucose by lactate or ethanol fermentation 36 ATP 2 ATP
Summary of ATP Formation in Aerobic Cellular Respiration
5.3 Cellular Respiration Releases Energy from Organic Compounds In muscle that is functioning anaerobically, pyruvate is converted to lactate and the reduced NADH is reoxidized so that glycolysis can continue. This process is called fermentation.
5.3 Cellular Respiration Releases Energy from Organic Compounds In yeast growing anaerobically, pyruvate is converted to carbon dioxide and ethanol. This process is known as ethanol fermentation.
5.3 Cellular Respiration Releases Energy from Organic Compounds Fermentation is used on an industrial scale to produce ethanol. Ethanol is used as an additive to gasoline to reduce some environmental contaminants. Selected Fermentation Products and their Uses
Summary of ATP Formation in Fermentation
Chapter 5 Review Ideas on how to review effectively?
Chapter 5 Review What molecule provides energy for most cellular processes? Would photosynthesis and respiration be able to proceed without enzymes? Why or why not? Where are chlorophyll molecules found? What happens when a compound is oxidized? Reduced? Which form contains more energy? What occurs during chemiosmosis? Where does it occur? What metabolic pathways are involved in cellular respiration? Where do they occur?
Chapter 5 Concept Organizer
Chapter 5 Summary Photosynthesis and cellular respiration proceed through dozens of different reactions to produce energy-rich compounds and break them down to release their stored energy in the form of ATP. Energy is contained in the bonds between the phosphate groups in ATP. When the bond to the last phosphate group is broken, leaving ADP and a free phosphate group, the energy released is available to do cellular work. In photosynthesis, the carbon dioxide and water are involved in two separate sets of reactions. Water is split into hydrogen ions, electrons, and oxygen in the lightdependent reactions. Carbon dioxide is incorporated into carbohydrates in the light-independent reactions.
Chapter 5 Summary (cont d) The light-dependent reactions in the thylakoid membranes capture light energy and use it to excite electrons that are chanelled away to produce ATP and NADPH. The light-independent reactions in the stroma use the chemical potential energy of ATP and the reducing power of NADPH to reduce carbon dioxide and form glucose and other carbohydrates via the Calvin- Benson cycle. Glucose is processed to release energy through glycolysis, the Krebs cycle, and electron transport. Glycolysis is an anaerobic process that occurs in the cytoplasm and breaks down glucose into pyruvate. Pyruvate enters the mitochondria, where it is broken down into carbon dioxide and acetyl CoA.
Chapter 5 Summary (cont d) Acetyl CoA enters the Krebs cycle in the matrix and energy released from breakdown of compounds in the Krebs cycle is used to reduce NAD+ and FAD. NADH and FADH2 donate electrons to the electron transport chain in the inner mitochondrial membranes. Energy released as electrons are passed along the chain is used to create a hydrogen ion gradient that powers chemiosmosis, which generates ATP. Glycolysis is the only source of energy for some organisms. Pyruvate is broken down into carbon dioxide and alcohol (ethanol fermentation) or lactate (lactate fermentation). This process occurs anaerobically.