Chapter 9

Summary		Questions		Media Resources
9.1 Cells harvest the energy in chemical bonds.
• The reactions of cellular respiration are oxidation-reduction (redox) reactions. Those that require a net input of free energy are coupled to the cleavage of ATP, which releases free energy. • The mechanics of cellular respiration are often dictated by electron behavior, which is in turn influenced by the presence of electron acceptors. Some atoms, such as oxygen, are very electronegative and thus behave as good oxidizing agents.		1.  What is the difference between an autotroph and a heterotroph? How does each obtain energy? 2.  What is the difference between digestion and catabolism? Which provides more energy?
9.2 Cellular respiration oxidizes food molecules.
• In the absence of oxygen, inorganic or organic molecules are used as the final electron acceptor and ATP is formed through substrate-level phosphorylation. • In eukaryotic cells, the oxidative respiration of pyruvate takes place within the matrix of mitochondria. • The electrons generated in the process are passed along the electron transport chain, a sequence of electron carriers in the inner mitochondrial membrane. • Some of the energy released by passage of electrons along the electron transport chain is used to pump protons out of the mitochondrial matrix. The reentry of protons into the matrix is coupled to the production of ATP. This process is called chemiosmosis. The ATP then leaves the mitochondrion by facilitated diffusion.		3.  Where in a eukaryotic cell does glycolysis occur? What is the net production of ATP during glycolysis, and why is it different from the number of ATP molecules synthesized during glycolysis? 4.  By what two mechanisms can the NADH that results from glycolysis be converted back into NAD+? 5.  What is the theoretical maximum number of ATP molecules produced during the oxidation of a glucose molecule by these processes? Why is the actual number of ATP molecules produced usually lower than the theoretical maximum?		•Exploration: Oxidative Respiration •Aerobic Cellular Respiration •Electron Transport and ATP A •Electron Transport and ATP B •Glycolysis •Krebs Cycle •Electron Transport •Activity: The Krebs Cycle •Activity:The Electron Transport Chain •Substrate-Level Phosphorylation •Catabolic vs. Anabolic Pathways •Pyruvate Pathways •Electron Transport System •Overview of ATP Synthesis •ATP Theoretical Yield
9.3 Catabolism of proteins and fats can yield considerable energy.
• The catabolism of proteins begins with the removal of the amino group from the amino acids through a process called deamination. The remaining carbon chain funnels into glycolysis or the Krebscycle. • The catabolism of fatty acids begins with b-oxidation and provides more energy than the catabolism of carbohydrates.		6.  How is acetyl-CoA produced during the aerobic oxidation of carbohydrates, and what happens to it? How is it produced during the aerobic oxidation of fatty acids, and what happens to it then?		• Catabolism of Proteins and Fats
9.4 Cells can metabolize food without oxygen.
• Fermentation is an anaerobic process that uses an organic molecule instead of oxygen as a final electron acceptor. • Fermentation occurs in bacteria as well as eukaryotic cells, including yeast and the muscle cells of animals.		7.  What is the efficiency of aerobic oxidation of glucose compared to that of anaerobic fermentation?		•Fermentation

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