Week 2 Course Lecture Ch 5

This PowerPoint will cover Chapter 5  WEEK 2 CLO’S CLO 1: Compare and contrast the cellular characteristics of the various prokaryotic and eukaryotic microorganisms (including helminths) CLO 4: Distinguish infectious diseases of microbial origin, including information about their...

This PowerPoint will cover Chapter 5  WEEK 2 CLO’S CLO 1: Compare and contrast the cellular characteristics of the various prokaryotic and eukaryotic microorganisms (including helminths) CLO 4: Distinguish infectious diseases of microbial origin, including information about their causative agent(s), signs and symptoms, diagnostic markers, treatment, and prevention 1/16/2025 2 Basic Chemical Reactions Underlying Metabolism Metabolism Collection of controlled biochemical reactions that take place within a microbe Ultimate function of metabolism is to reproduce the organism Basic Chemical Reactions Underlying Metabolism Metabolic Processes Guided by Eight Elementary Statements Every cell acquires nutrients. Metabolism requires energy from light or catabolism of nutrients. Energy is stored in adenosine triphosphate (ATP). Cells catabolize nutrients to form precursor metabolites. Precursor metabolites, energy from ATP, and enzymes are used in anabolic reactions. Enzymes plus ATP form macromolecules. Cells grow by assembling macromolecules. Cells reproduce once they have doubled in size. Metabolism: Overview PLAY PLAY Figure 5.1 Metabolism is composed of catabolic and anabolic reactions. Basic Chemical Reactions Underlying Metabolism Oxidation and Reduction Reactions Transfer of electrons from an electron donor to an electron acceptor Reactions always occur simultaneously. Cells use electron carriers to carry electrons (often in H atoms). Three important electron carriers: Nicotinamide adenine dinucleotide (NAD+) Nicotinamide adenine dinucleotide phosphate (NADP+) Flavin adenine dinucleotide (FAD) H2 + A → 2HA (Reduced) Na + Cl → Na+ + Cl- (Redox) (Cl is reduced, Na is oxidized) O2 + A → 2AO Figure 5.2 Oxidation-reduction, or redox, reactions. Basic Chemical Reactions Underlying Metabolism ATP Production and Energy Storage Organisms release energy from nutrients. Can be concentrated and stored in high-energy phosphate bonds (ATP) Phosphorylation—inorganic phosphate is added to substrate. Anabolic pathways use some energy of ATP by breaking a phosphate bond. Basic Chemical Reactions Underlying Metabolism The Roles of Enzymes in Metabolism Enzymes are organic catalysts. Increase likelihood of a reaction PLAY PLAY Enzymes: Overview Table 5.1 Enzyme Classification Based on Reaction Types Figure 5.6 The process of enzymatic activity. Basic Chemical Reactions Underlying Metabolism The Roles of Enzymes in Metabolism Enzyme activity Many factors influence the rate of enzymatic reactions: Temperature pH Enzyme and substrate concentrations Presence of inhibitors Figure 5.7a representati ve effects of temperature , pH, and substrate concentratio n on enzyme activity. figure 5.8 denaturation of protein enzymes. Figure 5.7b-c representative effects of temperature, pH, and substrate concentration on enzyme activity. Basic Chemical Reactions Underlying Metabolism The Roles of Enzymes in Metabolism Enzyme activity Control of enzymatic activity Activators Some enzymes are activated when a cofactor binds to a site other than the active site. Figure 5.9 Allosteric activation. Basic Chemical Reactions Underlying Metabolism The Roles of Enzymes in Metabolism Enzyme activity Control of enzymatic activity Inhibitors Substances that block an enzyme’s activity Include competitive and noncompetitive inhibitors Feedback inhibition controls the action of some enzymes. Basic Chemical Reactions Underlying Metabolism Tell Me Why How can oxidation take place in an anaerobic environment, that is, without oxygen?  Carbohydrate Catabolism Many organisms oxidize carbohydrates as primary energy source for anabolic reactions. Glucose is the most common carbohydrate used. Glucose is catabolized by two processes: Cellular respiration Fermentation Carbohydrate Catabolism Cellular Respiration Resultant pyruvic acid completely oxidized to produce ATP by series of redox reactions Three stages of cellular respiration: 1. Glycolysis and Synthesis of acetyl-CoA 2. Krebs cycle 3. Final series of redox reaction (electron transport chain) Figure 5.13 Summary of glucose catabolism. Carbohydrate Catabolism Glycolysis Occurs in cytoplasm of most cells Involves splitting of a six-carbon glucose into two three-carbon sugar molecules Substrate-level phosphorylation—direct transfer of phosphate between two substrates Net gain of two ATP molecules, two molecules of NADH, and precursor metabolite pyruvic acid Figure 5.14 Glycolysis by the EMP pathway. Figure 5.15 Example of substrate-level phosphorylation. Interactive Microbiology In the Interactive Microbiology tutorial in Chapter 5, we learn about aerobic respiration in prokaryotes. Jane’s elderly father is in the hospital with tuberculosis. He was previously treated for tuberculosis; why is it back? Tuberculosis is caused by Mycobacterium tuberculosis. Oxygen is needed for aerobic respiration, which includes glycolysis, the Kreb’s cycle, and electron transport. Without oxygen, M. tuberculosis is dormant in tubercles. When the tubercles rupture, M. tuberculosis has energy to grow, causing a reinfection in the lungs. Figure 5.16 The pyruvate dehydrogenase complex. Carbohydrate Catabolism Cellular Respiration Synthesis of acetyl-CoA Results in: Two molecules of acetyl-CoA Two molecules of CO2 Two molecules of NADH Carbohydrate Catabolism Cellular Respiration The Krebs cycle Great amount of energy remains in bonds of acetyl-CoA Transfers much of this energy to coenzymes NAD+ and FAD Occurs in cytosol of prokaryotes and in matrix of mitochondria in eukaryotes Figure 5.17 The Krebs cycle. Krebs Cycle: Overview PLAY PLAY Krebs Cycle: Overview Krebs Cycle: Steps PLAY PLAY Krebs Cycle: Steps Carbohydrate Catabolism Cellular Respiration The Krebs cycle Results in: Two molecules of ATP Two molecules of FADH2 Six molecules of NADH Four molecules of CO2 Carbohydrate Catabolism Cellular Respiration Electron transport Most significant production of ATP occurs from series of redox reactions known as an electron transport chain (ETC) Series of carrier molecules that pass electrons from one to another to final electron acceptor Energy from electrons used to pump protons (H+) across the membrane, establishing a proton gradient Located in inner mitochondrial membrane of eukaryotes and in cytoplasmic membrane of prokaryotes Figure 5.18a One possible arrangement of electron transport chain molecules. PLAY PLAY Electron Transport Chain: Overview Carbohydrate Catabolism Cellular Respiration Electron transport Aerobic respiration: oxygen serves as final electron acceptor. Anaerobic respiration: molecule other than oxygen serves as final electron acceptor. Figure 5.18b One possible arrangement of electron transport chain molecules. PLAY PLAY Electron Transport Chain: The Process PLAY Electron Transport Chain: PLAY Factors Affecting ATP Yield Carbohydrate Catabolism Cellular Respiration Chemiosmosis Use of electrochemical gradients to generate ATP Cells use energy released in redox reactions of ETC to create proton gradient. Protons flow down electrochemical gradient through ATP synthases that phosphorylate ADP to ATP. Called oxidative phosphorylation because proton gradient is created by oxidation of components of ETC Total of ~36-38 ATP molecules formed from one molecule of glucose Table 5.3 Summary of Ideal Prokaryotic Aerobic Respiration of One Molecule of Glucose Carbohydrate Catabolism Fermentation Sometimes cells cannot completely oxidize glucose by cellular respiration. Cells require constant source of NAD+. Cannot be obtained simply using glycolysis and Krebs cycle Fermentation pathways provide cells with alternative source of NAD+. Partial oxidation of sugar (or other metabolites) to release energy using an organic molecule from within the cell as final electron acceptor Figure 5.19 Examples of fermentation. Table 5.4 Comparison of Aerobic Respiration, Anaerobic Respiration, and Fermentation Figure 5.20 Representative fermentation products and the organisms that produce them. Fermentation PLAY PLAY Fermentation Other Catabolic Pathways Lipids and proteins contain energy in their chemical bonds. Can be converted into precursor metabolites Serve as substrates in glycolysis and the Krebs cycle Figure 5.21 Catabolism of a triglyceride molecule. Figure 5.22 Protein catabolism. Table 5.5 A Comparison of the Three Types of Phosphorylation Other Anabolic Pathways Anabolic reactions are synthesis reactions requiring energy and a source of precursor metabolites. Energy derived from ATP from catabolic reactions Many anabolic pathways are the reverse of catabolic pathways. Reactions that can proceed in either direction are amphibolic. Table 5.6 The 12 Precursor Metabolites Figure 5.27 The role of gluconeogenesis in the biosynthesis of complex carbohydrates. Figure 5.28 Biosynthesis of a triglyceride fat, a lipid. Figure 5.30 The biosynthesis of nucleotides. Integration and Regulation of Metabolic Function Cells synthesize or degrade channel and transport proteins. Cells often synthesize enzymes only when substrate is available. Cells catabolize the more energy-efficient choice if two energy sources are available. Cells synthesize metabolites they need, cease synthesis if metabolite is available. Integration and Regulation of Metabolic Function Two Types of Regulatory Mechanisms Control of gene expression Cells control amount and timing of protein (enzyme) production. Control of metabolic expression Cells control activity of proteins (enzymes) once produced. Figure 5.31 Integration of cellular metabolism (shown in an aerobic organism) PLAY PLAY Metabolism: The Big Picture Integration and Regulation of Metabolic Function Tell Me Why Why is feedback inhibition necessary for controlling anabolic pathways?