Energy - Releasing Pathways: Energy - Releasing Pathways Starr/Taggart’s Biology: The Unity and Diversity of Life, 9e Chapter 8


Key Concepts:: Key Concepts: All organisms can release energy stored in glucose and other compounds and use it in ATP production Glycolysis can occur with or without oxygen Fermentation is an anaerobic process and occurs in the cytoplasm Aerobic respiration yields more energy from glucose and occurs in the mitochondria


Key Concepts:: Key Concepts: Aerobic respiration has three stages Photosynthesis and aerobic respiration are linked on a global scale Sunlight -----> Photosynthesis C6H12O6 + 6O2 Aerobic Respiration 6CO2 + 6 H2O


How Cells Make ATP: How Cells Make ATP Photosynthesis Glycolysis Aerobic Pathways Anaerobic Pathways Fermentation


Overview of Aerobic Respiration: Overview of Aerobic Respiration Most ATP produced Yield of 36 ATP or more Summary: C6H12O6 + 6O2 ------> 6CO2 + 6 H2O Glucose Oxygen Carbon Dioxide Water


Respiration: Respiration Glycolysis In cytoplasm Krebs Cycle In mitochondria Electron Transport System In mitochondria


Glycolysis: Glycolysis Glucose to Pyruvate 2 ATP needed to start process Substrate-level Phosphorylation NAD+ ---> NADH End-Product 2 molecules of pyruvate


Glycolysis: Glycolysis


Glycolysis: Glycolysis


Second Stage of the Aerobic Pathway: Second Stage of the Aerobic Pathway Pyruvate enters mitochondria Krebs Cycle Inner compartment Electron Transport Inner membrane


Second Stage Reactions: Preparatory Steps : Second Stage Reactions: Preparatory Steps Pyruvate is stripped of a carboxyl group which departs as carbon dioxide It also gives up hydrogen and electrons to NADP+ to form NADPH Coenzyme A joins with remaining two-carbon fragment to form acetyl-CoA


Krebs Cycle: Krebs Cycle Acetyl-CoA transfers its two carbon fragment to oxaloacetate to start the cycle During the cycle - NAD+ and FAD are reduced to NADH and FADH2 Phosphate-level phosphorylation produces ATP Oxaloacetate is regenerated Carbon dioxide is released


Electron Transport Phosphorylation: Electron Transport Phosphorylation Innner membrane H+ concentration and electrical gradients ATP Synthases Formation of ATP from ADP and Pi by H+ flow


Summary of the Energy Harvest: Summary of the Energy Harvest Glycolysis 2 ATP by substrate-level phosphorylation 2 NADH (used to form 4 ATP during third stage) Krebs Cycle 2 ATP by substrate-level phosphorylation Electron Transport Phosphorylation 28 ATP by electron transport phosphorylation


Anaerobic Routes of ATP Formation: Anaerobic Routes of ATP Formation Fermentation pathways Bacteria, yeasts and protistans Glycolysis - first step Net yield of two ATP Final product is lactate or ethanol


Lactate Fermentation: Lactate Fermentation Muscle cells in animals Quick ATP production Some bacteria


Alcohol Fermentation: Alcohol Fermentation Acetaldehyde is intermediate product Yeasts


Anaerobic Electron Transport: Anaerobic Electron Transport Some bacteria Cycling of sulfur, nitrogen and others In plasma membrane Inorganic compound serves as final electron acceptor


Alternative Energy Sources in the Human Body: Alternative Energy Sources in the Human Body Carbohydrates Production of ATP from metabolism Excess stored as glycogen in liver and muscle cells Fats Triglycerides Stored in adipose tissue Can be used for energy Proteins Growth, maintenance, repair Can be used for ATP production


In Conclusion: In Conclusion Aerobic respiration, fermentation, and other pathways release energy that produce ATP NAD+ is the main coenzyme. FAD also is involved Oxidation - reduction reactions are involved Glycolysis is the start to all the pathways Net yield of Glycolysis is 2 ATP


In Conclusion: In Conclusion Aerobic respiration involves two more stages: Krebs cycle and electron transport phosphorylation These steps proceed in the mitochondria Oxaloacetate combines with Acetyl-CoA to start the Krebs cycle The electron transport system involves delivery of H+ by coenzymes


In Conclusion: In Conclusion H+ accumulate and gradients form across the membrane Energy released during H+ flow drives the formation of ATP Oxygen combines with H+ to form water Aerobic respiration yields 36 ATP for each glucose molecule metabolized Fermentation is an anaerobic process Lactate fermentation yields 2 ATP


In Conclusion: In Conclusion Alcohol fermentation yields 2 ATP Some bacteria use anaerobic electron transport with inorganic compounds as the final electron acceptor In some animals, sugars, fats, and amino acids can enter the ATP-producing pathways developed by M. Roig