Fig. 9.1 Respiration

Cellular Energy Harvest: an Overview Stages of Aerobic Cellular Respiration –Glycolysis –Oxidation of Pyruvate –Krebs Cycle –Electron Transport Chain Anaerobic Respiration and Fermentation Catabolism of Protein and Fat Outline – Cellular Respiration

Autotrophs – use inorganic sources of energy Photoautotrophs –harvest sunlight –convert radiant energy into chemical energy. Heterotrophs – use organic sources of energy –live off the energy produced by autotrophs. –extract energy from food catabolism Energy to Drive Metabolism

Cellular 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 Fermentation - final electron acceptor is an organic molecule

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Glucose molecules broken down to CO 2 Glucose loses electrons (as hydrogen atoms) to oxygen Cells tap energy from electrons Cells bank energy in ATP C 6 H 12 O 6 6 O 2 6 CO 2 6 H 2 O Loss of hydrogen atoms (oxidation) Gain of hydrogen atoms (reduction) Energy (ATP) Glucose + ++ Cellular Aerobic Respiration

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Oxidation - Dehydrogenase removes electrons from substrate Reduction - Electrons in Hydrogen Transferred to NAD + O H H O 2H Reduction Dehydrogenase (Enzyme) (carries 2 electrons) NAD  2H 2H  2e  NADH HH Oxidation Transferring Energy

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings H2OH2O NAD  NADH ATP HH HH Controlled release of energy for ATP synthesis Electron Transport Chain O2O2 2e   1. NADH passes electrons to an electron transport chain 2. Energy is released as electrons “fall” and lose energy Transferring Energy – Electron Transport Chain

Fig. 9.5 (TEArt) Mitochondrion Krebs cycle Glucose Glycolysis Pyruvate Acetyl- CoA ATP NADH FADH 2 Electron transport chain H2OH2O CO 2 NAD + and FAD Mitochondrial matrix Inner mitochondrial membrane Cytoplasm Intermembrane space e-e- Pyruvate oxidation CO 2 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Aerobic Cellular Respiration – Overview 1.Glycolysis 2.Pyruvate oxidation 3.Krebs (Citric Acid) Cycle 4.Electron Transport Chain

Fig. 9.6 (TEArt) Aerobic Respiration Stage 1: Glycolysis 123 (Starting material) 6-carbon sugar diphosphate 6-carbon glucose 2 PP 6-carbon sugar diphosphate PP 3-carbon sugar phosphate PPPP Priming reactions. 3-carbon pyruvate 2 NADH ATP 2 NADH ATP Cleavage reactions. Energy-harvesting reactions. 3-carbon sugar phosphate 3-carbon sugar phosphate 3-carbon sugar phosphate 3-carbon pyruvate Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Fig. 9.7a (TEArt) PiPi 3 6 4,5 ADP NAD + Glucose Glycolysis Pyruvate oxidation Krebs cycle Electron transport chain Glucose Hexokinase Phosphoglucose isomerase Phosphofructokinase Glyceraldehyde 3 -phosphate (G3P) Dihydroxyacetone phosphate Glucose 6-phosphate Fructose 6-phosphate Fructose 1,6-bisphosphate Isomerase Glyceraldehyde 3-phosphate dehydrogenase Aldolase 1,3-Bisphosphoglycerate (BPG) 1,3-Bisphosphoglycerate (BPG) 1. Priming 4–5. Six-carbon molecule split into 2 three-carbon molecules one G3P & dhap which is converted to G3P 1 2 ATP ADP ATP NADH NAD + NADH 6. Oxidation followed by phosphorylation produces two NADH molecules and two molecules of BPG, each with one high-energy phosphate bond. PiPi P OCH 2 CO CH 2 OH PO CH 2 OP O CHOH C CH 2 OP O CHOH CH 2 OP O OP O P O H CH 2 OH O CH 2 P O O CH 2 OH Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Glycolysis - Steps 2. Cleavage 1. Priming 3. Energy Harvest C

Fig. 9.7b (TEArt) 7 8 H2OH2O 9 10 ADP ATP 3-Phosphoglycerate (3PG) 3-Phosphoglycerate (3PG) 2-Phosphoglycerate (2PG) 2-Phosphoglycerate (2PG) Phosphoenolpyruvate (PEP) Phosphoenolpyruvate (PEP) Pyruvate 7. Removal of high-energy phosphate by two ADP molecules produces two ATP molecules and leaves two 3PG molecules. Phosphoglycerate kinase Phosphogly- ceromutase Enolase Pyruvate kinase ADP ATP ADP ATP ADP ATP 8–9. Removal of water yields two PEP molecules, each with a high-energy phosphate bond. 10. Removal of high-energy phosphate by two ADP molecules produces two ATP molecules and two pyruvate molecules. H2OH2O CH 2 OH CH 3 CH 2 O-O- O C PH CHOH O-O- O-O- O-O- C C C C C C P P O O O O O O CH 2 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Glycolysis - Steps 3. Energy Harvest Pyruvate 1,3-Bisphosphoglycerate (BPG)

 Catabolic pathway with 3 major events 1.Priming 2.Cleavage 3.Energy Harvesting Substrate-level phosphorylation  Nets two ATP molecules  Universal: All living organisms Glycolysis - Summary

Aerobic Respiration Stage 2 Oxidation of Pyruvate 1.Releases CO 2 2.Produces NADH and acetyl Coenzyme A 3.Acetyl CoA is transferred to the mitochondrion

Aerobic Respiration Stage 3: KREBS CYCLE Mitochondrion

Krebs Cycle Summary 1.Location: Mitochondrial matrix 2.Loss of 2 CO 2 = completion of pyruvate oxidation 3.ATP synthesis 4.Reduction of Coenzymes…for each turn of cycle:  3 NAD +  3 NADH… or 6 for each glucose  1 FAD  1 FADH 2 …or 2 for each glucose

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Mitochondrion Structure Outer Membrane Inner Membrane Cristae Matrix Intermembrane Space

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 1.Electron Flow occurs in mitochondrial membrane 2.Protons are transported across the inner mitochondrial membrane 3.ATP is synthesized by Chemiosmosis Intermembrane space Inner mitochondrial membrane Mitochondrial matrix Protein complex Electron carrier NAD + FAD H2OH2O ATP ADP ATP synthase H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+  P O2O2 Electron Transport Chain Chemiosmosis. OXIDATIVE PHOSPHORYLATION + NADH FADH 2 H+H+ H+H+ Stage 4: Oxidative Phosphorylation

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 1.Occurs in the mitochondria 2.Uses the energy released by electrons to pump H + across a membrane 3.Harnesses the energy of the H + gradient through chemiosmosis, producing ATP Stage 4: Oxidative Phosphorylation

Oxidation-Reduction and Aerobic Respiration

–With continuous Glycolysis NADH Increases NAD + Decreases –NADH must be recycled into NAD + Recycling NADH

Fermentation: Recycling NADH

22 Summary: Respiration without oxygen 1. Glycolysis produces a net of 2ATP 2. Fermentation - recycles NADH to NAD + Lactic acid fermentation CO 2 and Ethanol fermentation 3. Anaerobic Respiration Methanogens CO 2  CH 4 Sulfate-reducing Bacteria SO 4  H 2 S

2 2 6 ATP Pyruvate Glucose Acetyl-CoA NADH 2 4 ATP NADH 2 ATP ATPNADH 2 4ATP Total net ATP yield = 36ATP FADH2 Krebs cycle ATPGlycolysis Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Respiration Efficiency

Fig (TEArt) Macromolecules Cell building blocks Nucleic acids Proteins Fats Polysaccharides Nucleotides Amino acids Fatty acids Sugars NH 3 H2OH2OCO 2 Oxidative respiration Metabolic Waste products Pyruvate Acetyl-CoA Krebs cycle Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Energy Sources for Cellular Respiration

END Respiration