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* * * * * * CO2 H2O cristae intermembrane space matrix outer membrane Inner membrane double membrane 7.1 What’s Cellular Respiration?Produces ATP moleculesCarbon dioxide waste product (breathe)Essentially the reverse of photosynthesis Oxidation = removal of hydrogen atoms Hydrogens removed from glucose Gives waste product carbon dioxide Reduction = addition of hydrogen atoms Oxygen accepts hydrogens Become waste product water + + + Reduction 36 ATP 6 H2O 6 CO2 6 O2 glucose C6H12O6 Oxidation Figure 7.2 The four phases of complete glucose breakdown 2 2 3 4 e– O2 O2 Cytoplasm Glycolysis glucose pyruvate ATP CO2 ATP CO2 ATP H2O e– e– e– NADH and FADH2 Electron transport chain Citric acid cycle Preparatory reaction Phases of complete glucose breakdown Glucose broken down slowly in steps Energy captured and used to make ATP Coenzymes (nonprotein helpers) join with hydrogen NAD+ → NADH FAD → FADH2 Glycolysis In eukaryotes, takes place in the cytoplasm Glucose (6 carbons) broken down into two molecules of pyruvate (3 carbon) Divided into… Energy-investment steps Energy-harvesting steps Figure 7.3 Glycolysis e– 2 2 34 NADH and FADH2 Citric acid cycle Electron transport chain Cytoplasm Glycolysis ATP ATP ATP Preparatory reaction Energy-investment steps 2 ATP transfer phosphates to glucose Activates them for next steps Figure 7.3 P P P P Energy-investment step glucose –2 ATP ATP ATP G3P G3P 3PG BPG G3P 3-phosphoglycerate 1,3-bisphosphoglycerate glyceraldehyde-3-phosphate ADP ADP Figure 7.3 Energy-harvesting-steps Substrate-level ATP synthesis produces 4 ATP Net gain of 2 ATP 2 NADH made P P P P P + 2 A T P NAD+ P P H 2 O P P P P P H 2 O NADH NADH NAD+ –2 ATP ATP ATP ADP ADP G3P G3P 3PG 3PG ATP ATP ADP ADP BPG BPG Net gain: 2 ATP 3PG BPG G3P 3-phosphoglycerate 1,3-bisphosphoglycerate glyceraldehyde-3-phosphate pyruvate pyruvate Energy-harvesting steps P P P ATP ADP substrate enzyme Glycolysis totals Next step depends on oxygen availability With oxygen, pyruvate enters mitochondria Without oxygen, pyruvate undergoes reduction + 4 P Glycolysis inputs outputs glucose 2 pyruvate 2 NAD+ 2 NADH 2 ADP 2 ATP 4 ADP 4 ATP net 2 ATP 7.3 Inside the Mitochondria Other 3 phases take place inside the mitochondria Figure 7.5 Mitochondrion structure and function Figure 7.6 cytoplasm location of glycolysis cristae matrix outer membrane Inner membrane forms cristae Inter membrane space cristae location of the electron transport chain matrix location of the prep reaction and the citric acid cycle e– 2 2 Preparatory reaction NADH and FADH2 ATP 34 ATP matrix Electron transport chain Citric acid cycle Preparatory reaction ATP Glycolysis Preparatory reaction Occurs in mitochondrial matrix Produces a substrate that enters the citric acid cycle Occurs twice per glucose molecule Pyruvate oxidized, CO2 molecule given off NAD+ → NADH Two carbon acetyl group attached to CoA to give acetyl-CoA 2 2 2 Citric acid cycle inputs outputs 2 FAD 6 NAD+ 2 acetyl-CoA 2 FADH2 6 NADH 4 CO2 2NAD+ 2CoA 2CoA 2 CO2 Preparatory reaction NADH Pyruvate from glycolysis is oxidized to a C2 acetyl group that is carried by CoA to the citric acid cycle. 1 pyruvate 2ATP 2 ADP + 2 P 2 acetyl-CoA Citric Acid Cycle (Krebs Cycle) Occurs in matrix of mitochondria Acetyl CoA transfer acetyl group to C4 molecule – produces citric acid (6 carbons) CoA returns to preparatory reaction for reuse Acetyl group oxidized to carbon dioxide NAD+ → NADH and FAD → FADH2 Substrate-level ATP synthesis produces ATP Two cycles for each glucose molecule Citric acid cycle inputs outputs 2 FAD 6 NAD+ 2 acetyl-CoA 2 FADH2 6 NADH 4 CO2 2ATP 2 ADP + 2 P 2 2 2 Citric acid cycle inputs outputs 2 FAD 6 NAD+ 2 acetyl-CoA 2 FADH2 6 NADH 4 CO2 Each C2 acetyl group combines with a C4 molecule to produce citric acid, a C6 molecule. 2NAD+ 2CoA 2CoA NADH NAD+ Twice, oxidation reactions produce NADH, and CO2 is released. CO2 3 2 NADH CO2 NAD The loss of two CO2 results in a new C4 molecule. 4 5 ATP is produced by substrate-level ATP synthesis. ATP FADH2 NADH FAD NAD+ ADP + P Citric acid cycle 6 Additional oxidation reactions produce another NADH and an FADH2 and regenerate the original C4 2 CO2 Preparatory reaction NADH Pyruvate from glycolysis is oxidized to a C2 acetyl group that is carried by CoA to the citric acid cycle. 1 pyruvate 2ATP 2 ADP + 2 P Figure 7.6 Krebs Cycle Oxaloacetate 2 acetyl-CoA Electron Transport Chain Located in cristae of mitochondria Series of carriers pass electrons from one to the other NADH and FADH2 deliver electrons Hydrogen atoms attached consist of e- and H+ Carriers accept only e- not H + e– 2 2 Glycolysis ATP Preparatory reaction NADH and FADH2 Citric acid cycle ATP 34 ATP Electron transport chain High-energy electrons enter/ low-energy electrons leave As pair of electrons passed from one carrier to the next, energy is released Will be captured as ATP Final electron acceptor is oxygen – forms water Figure 7.7 The electron transport chain O2 1 1 2 2 3 3 4 4 5 5 2 H+ O2 1 – 2 NADH and FADH2 NAD+ NADH 2H+ oxidized oxidized oxidized oxidized H2O 2e– 3 ATP H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H + H+ e– O2 2 1 – 2 matrix cristae intermembrane space a. Electron transport chain Matrix NADH FADH2 NAD+ H2O b. ATP synthesis ATP ATP synthase complex ADP + P mobile carrier electron transport carriers in a molecular complex FAD Intermembrane space Figure 7.8 The organization of cristae ATP synthesis carried out by ATP synthase in inner mitochondrial membrane Carriers of electron transport system pass electrons Energy used to pump H + from matrix into intermembrane space – creates H+ gradient ATP synthase uses energy to make ATP Energy yield from glucose metabolism Maximum of 38 ATP made Some cells make only 36 ATPs or less 36-38 ATP about 40% of available energy in a glucose molecule Rest is lost as heat Figure 7.9 Calculating ATP energy yield per glucose molecule – – 2 2 2 6 2 – 4 2 2 Phase NADH FADH2 ATP Yield Glycolysis Prep reaction Citric acid cycle Electron transport chain Total ATP 38 30 10 Alternative metabolic pathways Cells use other energy sources Fatty acids have longer carbon chains – yields more ATP Intermediates can also be used to make other products Extra food made into fat for storage Figure 7.10 Alternative metabolic pathways O2 Food Proteins Carbohydrates Fats and oils amino acids fatty acids glycerol glucose NH3 Glycolysis ATP pyruvate Acetyl-CoA Citric acid cycle ATP Electron transport chain ATP H2O Aerobic Respiration 7.4 Fermentation Oxygen is required for the complete breakdown of glucose Fermentation – anaerobic breakdown of glucose Generates only 2 ATP total Animal cells Pyruvate reduced to lactate Brief burst of energy for muscle cells Recovery from oxygen deficit complete when enough oxygen is present to completely break down glucose Lactate converted back to pyruvate or glucose Microorganisms and fermentation Bacteria use fermentation to produce Lactate or other organic acids Alcohol and carbon dioxide Yeast – carbon dioxide makes bread rise, ethanol made in wine and beer Fermentation inputs glucose 2 ATP 4 ADP + 4 P 4 ATP net 2 ATP 2 ADP 2 alcohol and 2 CO2 or 2 lactate outputs P 2 P 2 P P 2 2 glucose 2 ATP –2 ATP 2 ADP Glycolysis 2 NAD+ 2 NADH 4 ADP +4 ATP 4 ATP Fernentation pyruvate 2 NADH 2 NAD+ Net gain: 2 ATP 2CO2 Athlete Wine 2lactate 2ethyl alcohol or * * * * * * * * * * * * * * * * * * * * * * * * * * eturns to preparatory reaction for reuse Acetyl group oxidized to carbon dioxide NAD+ → NADH and FAD → FADH2 Substrate-level ATP synthesis produces ATP Two cycles for each glucose molecule Citric acid cycle inputs outputs 2 FAD 6 NAD+ 2 acetyl-CoA 2 FADH2 6 NADH 4 CO2 2ATP 2 ADP + 2 P 2 2 2 Citric acid cycle inputs outputs 2 FAD 6 NAD+ 2 acetyl-CoA 2 FADH2 6 NADH 4 CO2 Each C2 acetyl group combines with a C4 molecule to produce citric acid, a C6 molecule. 2NAD+ 2CoA 2CoA NADH NAD+ Twice, oxidation reactions produce NADH, and CO2 is released. CO2 3 2 NADH CO2 NAD The loss of two CO2 results in a new C4 molecule. 4 5 ATP is produced by substrate-level ATP synthesis. ATP FADH2 NADH FAD NAD+ ADP +