Outline Cellular Respiration

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1 Fig. 9.1 Respiration utline ellular Respiration ellular Energy Harvest: an verview Stages of Aerobic ellular Respiration Glycolysis xidation of yruvate Krebs ycle Electron Transport hain Anaerobic Respiration and Fermentation atabolism of rotein and Fat Energy to Drive Metabolism Autotrophs use inorganic sources of energy hotoautotrophs harvest sunlight convert radiant energy into chemical energy. hemoautotrophs harvest energy from inorganic sources S, NH 3, NH 2, H 2 S, Fe +2 ellular Respiration Metabolic pathways series of reactions oxidations loss of electrons dehydrogenations hydrogen atom (1 electron, 1 proton). Heterotrophs use organic sources of energy live off energy produced by autotrophs. extract energy from food catabolism Uusecellular respiration to extract energy 1

2 ellular Respiration How do cells harvest energy cells break chemical bonds shift electrons from molecule to molecule Where do the electrons go? Aerobic respiration final electron acceptor is oxygen Anaerobic respiration final electron acceptor is not oxygen ellular Aerobic Respiration Glucose molecules broken down to 2 Glucose loses electrons (as hydrogen atoms) to oxygen ells tap energy from electrons ells bank energy in Loss of hydrogen atoms (oxidation) 6 H H 2 + Glucose Gain of hydrogen atoms (reduction) () Energy ΔG = -686kcal/mol glucose Transferring Energy xidation - Dehydrogenase removes electrons from substrate Reduction - Electrons in Hydrogen Transferred to Transferring Energy Electron Transport hain 1. passes electrons to an electron transport chain 2. Energy is released as electrons fall and lose energy H H xidation Dehydrogenase + 2H (Enzyme) + 2e + 2 2H + 2e Reduction NAD (carries 2 electrons) Electron Transport hain 2e H 2 ontrolled release of energy for synthesis 2 2

3 Aerobic Respiration xidation of Glucose omplete oxidation of glucose proceeds in 4 stages 1. glycolysis 2. pyruvate oxidation 3. Krebs cycle (citric acid cycle) 4. electron transport chain & chemiosmosis opyright The McGraw-Hill ompanies, Inc. ermission required for reproduction or display. Fig. 9.6 (TEArt) Aerobic Respiration Stage 1: Glycolysis carbon glucose (Starting material) 2 6-carbon sugar diphosphate 6-carbon sugar diphosphate 3-carbon sugar 3-carbon sugar 3-carbon sugar 3-carbon sugar phosphate phosphate phosphate phosphate 2 2 riming reactions. leavage reactions. 3-carbon pyruvate 3-carbon pyruvate Energy-harvesting reactions. Fig. 9.7a (TEArt) Glucose Glycolysis yruvate oxidation Krebs cycle Electron transport chain 4 5. Six-carbon molecule split into 2 three-carbon molecules one G3 & dhap which is converted to G3 6. xidation followed by phosphorylation produces two molecules and two molecules of BG, each with one high-energy phosphate bond. opyright The McGraw-Hill ompanies, Inc. ermission required for reproduction or display. Glycolysis - Steps Glucose 1. riming 1 Hexokinase 1. riming AD Glucose 6-phosphate 2 hosphoglucose isomerase Fructose 6-phosphate 3 hosphofructokinase AD Fructose 1,6-bisphosphate H 2 4,5 Aldolase 2. leavage H Isomerase H 2 Dihydroxyacetone Glyceraldehyde 3 phosphate -phosphate (G3) HH H 2H H 6 i 2 i Glyceraldehyde 3. Energy Harvest 3-phosphate dehydrogenase 1,3-Bisphosphoglycerate 1,3-Bisphosphoglycerate HH (BG) (BG) H 2 H 2H H 2 H 2 H 2 H 2H Fig. 9.7b (TEArt) Glycolysis - Steps 7. Removal of high-energy phosphate by two AD molecules produces two molecules and leaves two 3G molecules Removal of water yields two E molecules, each with a high-energy phosphate bond. 10. Removal of high-energy phosphate by two AD molecules produces two molecules and two pyruvate molecules. opyright The McGraw-Hill ompanies, Inc. ermission required for reproduction or display. AD 3-hosphoglycerate (3G) 2-hosphoglycerate (2G) H 2 7 hosphoglycerate kinase 8 hosphoglyceromutase 9 Enolase hosphoenolpyruvate (E) 1,3-Bisphosphoglycerate (BG) AD 3-hosphoglycerate (3G) 2-hosphoglycerate (2G) H 2 hosphoenolpyruvate (E) 3. Energy Harvest H 2 H 2H AD 10 AD yruvate kinase 3. Energy Harvest yruvate yruvate H 3 H - HH - - H 2-3

4 Glycolysis - Summary Glycolysis = atabolic pathway 10 biochemical steps Major Stages 1. riming 2. leavage 3. Energy Harvesting Substrate-level phosphorylation Nets 2 molecules Nets 2 pyruvates Nets 2 Universal: All living organisms Aerobic Respiration Stage 2 xidation of yruvate 1. Releases 2 2. roduces and acetyl oenzyme A 3. Acetyl oa is transferred to the mitochondrion yruvate in cytoplasm uter mitochondrial membrane Inner mitochondrial membrane Aerobic Respiration Stage 3: KREBS YLE Krebs ycle Summary 1. Location: Mitochondrial matrix Mitochondrion 2. Loss of 2 2 = completion of pyruvate oxidation 3. synthesis 4. Reduction of oenzymes for each turn of cycle: 3 3 or 6 for each glucose 1 FAD 1 FADH 2 or 2 for each glucose 4

5 Glycolysis + yruvate xidation + Krebs ycle Mitochondrion Structure After glycolysis, pyruvate oxidation, and the Krebs cycle, glucose has been oxidized to: FADH 2 roceed to electron transport chain. Intermembrane Space ristae Inner Membrane uter Membrane Matrix Stage 4: xidative hosphorylation 1.Electron Flow occurs in mitochondrial membrane 2.rotons are transported across the inner mitochondrial membrane 3. is synthesized by hemiosmosis H 2. Intermembrane space H+ Stage 4: xidative hosphorylation Synthesis by hemiosmosis + H Inner mitochondrial membrane Mitochondrial matrix Figure 6.10 e - e - FADH 2 FAD Electron Transport hain H 2 Electron Transport hain AD hemiosmosis by synthase 5

6 Stage 4: xidative hosphorylation 1. ccurs in the mitochondria 2. Uses the energy released by electrons to pump across a membrane 3. Harnesses the energy of the gradient through chemiosmosis, producing xidation-reduction and Aerobic Respiration Fig. 9.5 (TEArt) FADH 2 Mitochondrion opyright The McGraw-Hill ompanies, Inc. ermission required for reproduction or display. Aerobic ellular Respiration verview Glucose Glycolysis yruvate yruvate oxidation Acetyl- oa Krebs cycle ytoplasm Glycolysis 2. yruvate oxidation 3. Krebs (itric Acid) ycle 4. Electron Transport hain Intermembrane space Mitochondrial matrix H 2 and FAD e - Electron transport chain Inner mitochondrial membrane Synthesis & xidation of Glucose Aerobic Respiration ells are able to make via: 1. substrate-level phosphorylation transferring a phosphate directly to AD from another molecule 2. oxidative phosphorylation use of synthase and energy derived from a proton ( ) gradient to make 6

7 Recycling With continuous Glycolysis Increases Decreases must be recycled into Fate of yruvate 1. aerobic respiration oxidized in mitochondria 2. anaerobic respiration oxidized another way fermentation = use of organic molecules as final electron acceptor anaerobic respiration = use of inorganic molecule as e - acceptor Sulfate-reducing bacteria Methanogenic bacteria Summary: Respiration without oxygen 1. Glycolysis produces a net of 2 2. Fermentation - recycles to Lactic acid fermentation 2 and Ethanol fermentation Respiration Efficiency 3. Anaerobic Respiration Methanogens 2 H 4 Sulfate-reducing Bacteria S 4 H 2 S 27 7

8 Fig (TEArt) Macromolecules opyright The McGraw-Hill ompanies, Inc. ermission required for reproduction or display. Energy Sources for ellular Respiration Nucleic acids roteins olysaccharides Fats ell building blocks Nucleotides Amino acids Sugars Fatty acids END yruvate Respiration xidative respiration Acetyl-oA Krebs cycle Metabolic Waste products NH 3 H 2 2 8