Fig. 7-2a, p.108

1. Fig. 7-2a, p.108

2. a All carbohydrate breakdown pathways start in the cytoplasm, with glycolysis. b Fermentation pathways are completed in the semifluid matrix of the cytoplasm. c In eukaryotes, aerobic respiration is completed inside mitochondria. Fig. 7-2b, p.108

3. Cytoplasm glucose a The first stage, glycolysis, occurs in the cell’s cytoplasm. Enzymes convert a glucose molecule to 2 pyruvate for a net yield of 2 ATP. During the reactions, 2 NAD+ pick up electrons and hydrogen atoms, so 2 NADH form. 2 ATP ATP 4 ATP (2net) ATP GLYCOLYSIS 2 pyruvate 2 NADH Mitochondrion 6 CO2 Krebs Cycle b The second stage, the Krebs cycle and a few steps before it, occurs inside mitochondria. The 2 pyruvates are broken down to CO2, which leaves the cell. During the reactions, 8 NAD+ and 2 FAD pick up electrons and hydrogen atoms, so 8 NADH and 2 FADH2 form. 2 ATP also form. ATP 2 ATP 8 NADH, 2 FADH2 ATP Electron Transfer Phosphorylation c The third and final stage, electron transfer phosphorylation, occurs inside mitochondria. 10 NADH and 2 FADH2 donate electrons and hydrogen ions at electron transfer chains. Electron flow through the chains sets up H+ gradients that drive ATP formation. Oxygen oxygen 32 ATP Fig. 7-3, p.109

4. glucose Glycolysis 2 ADP (net) 2 pyruvate 2 NADH to second stage of aerobic respiration or another pathway to third stage of aerobic respiration or another pathway Fig. 7-4b, p.110

5. glucose (glycolysis) 2 pyruvate outer membrane (next to cytoplasm) OUTER COMPARTMENT inner membrane INNER COMPARTMENT CO2 inner mitochondrial compartment 2 acetyl–CoA ATP Breakdown of 2 pyruvate to 6CO2 yields 2 ATP. Also, 10 coenzymes are reduced (8 NADH, 2 FADH2). The coenzymes carry hydrogen ions and electrons to sites of the third stage of aerobic respiration. NADH Krebs Cycle FADH2 outer mitochondrial compartment (in between the two membranes) a An inner membrane divides a mitochondrion’s interior into two compartments. The second and third stages of aerobic respiration take place at this membrane. b The second stage starts after membrane proteins transport pyruvate from the cytoplasm, across both mitochondrial membranes, to the inner compartment. Six carbon atoms enter these reactions (in two pyruvate), and six leave (in six CO2). Many coenzymes form. Fig. 7-5, p.112

6. Fig. 7-6, p.113

7. glucose Glycolysis you are here Krebs Cycle Electron Transfer Phosphorylation Fig. 7-6b, p.113

8. Fig. 7-7, p.114

9. glucose Glycolysis you are here Krebs Cycle Electron Transfer Phosphorylation Fig. 7-7a, p.114

10. glucose 2 ATP Glycolysis ATP (2 net) 2 NAD+ 2 pyruvate 2 NADH CYTOPLASM OUTER MITOCHONDRIAL COMPARTMENT INNER MITOCHONDRIAL COMPARTMENT 2 acetyl-CoA 2 NADH 2 CO2 2 NADH 4 CO2 6 NADH Krebs Cycle 2 ATP 2 FADH2 ADP + Pi Electron Transfer Phosphorylation water 32 ATP H+ H+ H+ H+ H+ oxygen Fig. 7-8, p.115

11. Fig. 7-9, p.116

12. Fig. 7-10a, p.117

13. Fig. 7-11, p.117

14. FOOD fats PROTEINS COMPLEX CARBOHYDRATES glycerol amino acids glucose, other simple sugars fatty acids acetyl-coA acetyl-coA PGAL Glycolysis NADH pyruvate oxaloacetate or another intermediate of the Krebs Krebs Cycle NADH, FADH2 Electron Transfer Phosphorylation Fig. 7-12a, p.119

15. sunlight energy in glucose (stored chemical energy) Aerobic Respiration Energy input from two ATP initiates three stages of reactions. Many ATP form during thecomplete breakdown of glucose to carbon dioxide and water. Photosynthesis chemical energy in many ATP available to drive nearly all cellular tasks Driven by energy input from the sun, electrons and hydrogen are used to form ATP. ATP energy drives the synthesis of glucose from hydrogen, electrons (delivered by coenzymes), and carbon dioxide’s atoms. carbon dioxide, water oxygen energy out (heat) energy out (heat) Fig. 7-13, p.120

16. 1 glucose ATP (net) Glycolysis pyruvate NADH ATP Krebs Cycle CO2 FADH2 Electron Transfer Phosphorylation ATP p.122