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Catabolic and Anabolic Reactions Metabolism: The sum of the chemical reactions in an organism Catabolic and Anabolic Reactions Catabolism: Provides energy and building blocks for anabolism. Anabolism: Uses energy and building blocks to build large molecules Role of ATP in Coupling Reactions Figure 5.1 Catabolic and Anabolic Reactions A metabolic pathway is a sequence of enzymatically catalyzed chemical reactions in a cell Metabolic pathways are determined by enzymes Enzymes are encoded by genes Collision Theory The collision theory states that chemical reactions can occur when atoms, ions, and molecules collide Activation energy is needed to disrupt electronic configurations Reaction rate is the frequency of collisions with enough energy to bring about a reaction. Reaction rate can be increased by enzymes or by increasing temperature or pressure Energy Requirements of a Chemical Reaction Figure 5.2 Enzyme Components Biological catalysts Specific for a chemical reaction; not used up in that reaction Apoenzyme: Protein Cofactor: Nonprotein component Coenzyme: Organic cofactor Holoenzyme: Apoenzyme plus cofactor Components of a Holoenzyme Figure 5.3 Important Coenzymes NAD+ NADP+ FAD Coenzyme A Enzyme Classification Oxidoreductase: Oxidation-reduction reactions Transferase: Transfer functional groups Hydrolase: Hydrolysis Lyase: Removal of atoms without hydrolysis Isomerase: Rearrangement of atoms Ligase: Joining of molecules, uses ATP Factors Influencing Enzyme Activity Temperature pH Substrate concentration Inhibitors Factors Influencing Enzyme Activity Temperature and pH denature proteins Figure 5.6 Effect of Temperature on Enzyme Activity Figure 5.5a Effect of pH on Enzyme Activity Figure 5.5b Enzyme Inhibitors: Competitive Inhibition Figure 5.7a–b Oxidation-Reduction Reactions Oxidation: Removal of electrons Reduction: Gain of electrons Redox reaction: An oxidation reaction paired with a reduction reaction Oxidation-Reduction Figure 5.9 Oxidation-Reduction Reactions In biological systems, the electrons are often associated with hydrogen atoms. Biological oxidations are often dehydrogenations. The Generation of ATP ATP is generated by the phosphorylation of ADP Substrate-Level Phosphorylation Energy from the transfer of a high-energy PO4– to ADP generates ATP Oxidative Phosphorylation Energy released from transfer of electrons (oxidation) of one compound to another (reduction) is used to generate ATP in the electron transport chain Photophosphorylation Light causes chlorophyll to give up electrons. Energy released from transfer of electrons (oxidation) of chlorophyll through a system of carrier molecules is used to generate ATP. Carbohydrate Catabolism The breakdown of carbohydrates to release energy Glycolysis Krebs cycle Electron transport chain Glycolysis The oxidation of glucose to pyruvic acid produces ATP and NADH Figure 5.11 Preparatory Stage of Glycolysis 2 ATP are used Glucose is split to form 2 glucose-3-phosphate Figure 5.12, steps 1–5 Energy-Conserving Stage of Glycolysis 2 glucose-3-phosphate oxidized to 2 pyruvic acid 4 ATP produced 2 NADH produced Figure 5.12, steps 6–10 Glycolysis Glucose + 2 ATP + 2 ADP + 2 PO4– + 2 NAD+ 2 pyruvic acid + 4 ATP + 2 NADH + 2H+ Cellular Respiration Oxidation of molecules liberates electrons for an electron transport chain ATP is generated by oxidative phosphorylation Intermediate Step Pyruvic acid (from glycolysis) is oxidized and decarboyxlated Figure 5.13 The Krebs Cycle Oxidation of acetyl CoA produces NADH and FADH2 The Krebs Cycle Figure 5.13 The Electron Transport Chain A series of carrier molecules that are, in turn, oxidized and reduced as electrons are passed down the chain Energy released can be used to produce ATP by chemiosmosis Overview of Respiration and Fermentation Figure 5.11 Chemiosmotic Generation of ATP Figure 5.16 An Overview of Chemiosmosis A Summary of Respiration Aerobic respiration: The final electron acceptor in the electron transport chain is molecular oxygen (O2). Anaerobic respiration: The final electron acceptor in the electron transport chain is not O2. Yields less energy than aerobic respiration because only part of the Krebs cycles operates under anaerobic conditions. Carbohydrate Catabolism Pathway Eukaryote Prokaryote Glycolysis Cytoplasm Cytoplasm Intermediate step Cytoplasm Cytoplasm Krebs cycle Mitochondrial matrix Cytoplasm ETC Mitochondrial inner membrane Plasma membrane Carbohydrate Catabolism Energy produced from complete oxidation of one glucose using aerobic respiration ATP Produced NADH Produced FADH2 Produced Glycolysis 2 2 0 Intermediate step 0 2 Krebs cycle 2 6 2 Total 4 10 2 Pathway Carbohydrate Catabolism ATP produced from complete oxidation of one glucose using aerobic respiration Pathway By Substrate-Level Phosphorylation By Oxidative Phosphorylation From NADH From FADH 0 Glycolysis 2 6 Intermediate step 0 6 Krebs cycle 2 18 4 Total 4 30 4 Carbohydrate Catabolism 36 ATPs are produced in eukaryotes Pathway By Substrate-Level Phosphorylation By Oxidative Phosphorylation From NADH From FADH 0 Glycolysis 2 6 Intermediate step 0 6 Krebs cycle 2 18 4 Total 4 30 4 Fermentation Any spoilage of food by microorganisms (general use) Any process that produces alcoholic beverages or acidic dairy products (general use) Any large-scale microbial process occurring with or without air (common definition used in industry) Fermentation Scientific definition: Releases energy from oxidation of organic molecules Does not require oxygen Does not use the Krebs cycle or ETC Uses an organic molecule as the final electron acceptor An Overview of Fermentation End-Products of Fermentation Figure 5.18b Fermentation Alcohol fermentation: Produces ethanol + CO2 Lactic acid fermentation: Produces lactic acid Homolactic fermentation: Produces lactic acid only Heterolactic fermentation: Produces lactic acid and other compounds A Fermentation Test Figure 5.23 Types of Fermentation Table 5.4 Types of Fermentation Table 5.4 Photosynthesis Figure 4.15 Photosynthesis Photo: Conversion of light energy into chemical energy (ATP) Light-dependent (light) reactions Synthesis: Carbon fixation: Fixing carbon into organic molecules Light-independent (dark) reaction: Calvin-Benson cycle Photosynthesis Oxygenic: 6 CO2 + 12 H2O + Light energy ® C6H12O6 + 6 H2O + 6 O2 Anoxygenic: 6 CO2 + 12 H2S + Light energy ® C6H12O6 + 6 H2O + 12 S Photosynthesis Compared Table 5.6 A Nutritional Classification of Organisms Figure 5.28 Metabolic Diversity among Organisms Nutritional Type Energy Source Carbon Source Example Photoautotroph Light CO2 Oxygenic: Cyanobacteria plants Anoxygenic: Green, purple bacteria Photoheterotroph Light Organic compounds Green, purple nonsulfur bacteria Chemoautotroph Chemical CO2 Iron-oxidizing bacteria Chemoheterotroph Chemical Organic compounds Fermentative bacteria Animals, protozoa, fungi, bacteria. The Integration of Metabolism Amphibolic pathways: Metabolic pathways that have both catabolic and anabolic functions Amphibolic Pathways Figure 5.33 Amphibolic Pathways Figure 5.33