MID MICROBIAL METABOLISM

MICROBIAL METABOLISM METABOLISM  Cells must accomplish two fundamental tasks to grow  Synthesize new components o   biosynthesis Harvest energy The sum total of chemical reactions of biosynthesis and energy-harvesting is termed metabolism PRINCIPLES OF METABOLISM    Metabolism is broken down into two components  Anabolism  Catabolism Catabolism  Degradative reactions produce energy from the break down of  Reactions larger molecules Anabolism  Reactions involved in the synthesis of cell components  Anabolic reactions require energy o Anabolic reactions utilize the energy produced from catabolic reactions PRINCIPLES OF METABOLISM  Harvesting energy  Energy defined as capacity to work  Exists as o Potential energy • o Stored energy Kinetic energy • Energy in motion   Doing work Energy can be converted from one form to another o o Potential  kinetic Kinetic  potential PRINCIPLES OF METABOLISM  Harvesting energy  Amount of energy released from the bonds is called free energy o Energy available to work • If reactants have more free energy than products, energy is released Exergonic reaction If products have more energy that reactants, energy is consumed  •  Endergonic reaction PRINCIPLES OF METABOLISM  Components of metabolic pathways  Process occurs in sequence of chemical reactions o Starting compound is converted to intermediate molecules and end products •  Intermediates and end products can be used as precursor metabolites Metabolic pathways employ critical components to complete processes o o o o o Enzymes ATP Chemical energy source Electron carriers Precursor metabolites PRINCIPLES OF METABOLISM  Role of enzymes   Enzymes facilitate each step of metabolic pathway They are proteins acting as chemical catalysts o  Accelerate conversion of substrate to product Catalyze reactions by lowering activation energy o Energy required to initiate a chemical reaction ENZYMES  Act as biological catalysts  Very specific o  Enzymes not alter the reactants or products of a chemical reaction o  A particular enzyme will only act with one or a limited number of substrates Enzymes are not altered by the chemical reaction they catalyze Enzymes are usually named for the substrate they act on and end in the suffix –ase o protease ENZYMES  Enzyme action  Enzymes act in two steps o Substrate binds to the active site of the enzyme to form an enzyme/substrate complex • o A substrate is the specific substance on which the enzyme acts Products are formed   E + S  ES  E + P Enzyme is released to bind new substrate  Enzymes are regulated to prevent over production of product ENZYMES  Cofactors and Coenzymes  Cofactors o  Non-protein component reacting with enzyme Coenzymes o Organic cofactors • Act as carriers for molecules or electrons  o NAD+, FAD and NADP+ are coenzymes Not as specific as enzymes • May act with numerous enzymes RESPIRATION  Uses NADH and FADH2 to synthesize ATP  Oxidative phosphorylation occurs through a combination of mechanisms o Electron transport chain • o Generates proton motive force Combined with ATP synthase • Uses energy in proton motive force to synthesize ATP RESPIRATION  Electron transport chain  Group of membrane-embedded electron carriers o  Arrangement of carriers aids in production of proton motive force Four types of electron carriers o o o o Flavoproteins—FAD Iron-sulfur proteins—like NAD dehydrogenase complex Quinones—lipid soluble molecules that move within the membrane and transfer electrons Cytochromes—proteins with a heme group RESPIRATION  Electron transport chain of mitochondria  Chain consists of following components o Complex I • o Complex II • o o o o  a.k.a NADH dehydrogenase a.k.a succinate dehydrogenase Coenzyme Q Complex III Cytochrome C Complex IV Each carrier accepts electrons from previous carrier o In process, protons are pumped across membrane ELECTRON TRANSPORT CHAIN OF MITOCHONDRIA RESPIRATION  Mechanism of proton force  Certain carriers accept protons and electrons, some accept only electrons o Pump protons across membrane • Creates a proton gradient • Arrangement of carriers causes protons to be shuttled across membrane RESPIRATION  The electron transport chain uses a series of oxidation reduction reactions to generate energy to pump H+ and to form water ELECTRON TRANSPORT CHAIN OF MITOCHONDRIA RESPIRATION  Electron transport chain of prokaryotes   Respiration is either aerobic or anaerobic In aerobic respiration some prokaryotes have enzymes equivalent to complex I and II of mitochondria o Do not have enzyme equivalents of complex III or cytochrome c • Use quinones instead (ubiquinone)   Shuttles electrons directly to terminal electron acceptor Oxygen acts as acceptor when available ELECTRON TRANSPORT CHAIN OF PROKARYOTES (AEROBIC) RESPIRATION  Electron transport chain in prokaryotes    Anaerobic respiration is less efficient Alternative electron carriers used Oxygen does not act as terminal electron acceptor o Some bacteria use nitrate • Nitrate converted to nitrite  o  Nitrite converted to ammonia Sulfur-reducer bacteria use sulfate as terminal electron acceptor Quinone carrier (menaquinone) produces vitamin K RESPIRATION  ATP synthase  Harvest energy from proton force to synthesize ATP o Permits protons to flow back into cell • Produces enough energy to phosphorylate ADP  ATP   10 protons pumped out per NADH+H o  One ATP is formed from entry of protons + One NADH produces molecules ATP protons pumped out per FADH2 o One FADH produces molecules of ATP RESPIRATION  ATP from oxidative phosphorylation   ATP produced through re-oxidation of NADH + H Maximum theoretical yield o From glycolysis • o From transition step • o NADH + H+  ATP NADH + H+ ATP From TCA • NADH + H+ 18 ATP • FADH2  ATP + and FADH2 FERMENTATION   Used by organisms that cannot respire  Due to lack of suitable inorganic electron acceptor or lack of electron transport chain  Other steps for consuming excess reducing power ATP produced only in glycolysis o o Recycles NADH Fermentation pathways use pyruvate or derivative as terminal electron acceptor FERMENTATION FERMENTATION   End products of fermentation can include       Lactic acid Ethanol Butyric acid Propionic acid 2,3-Butanediol Mixed acids All are produced in a series of reactions to produce appropriate terminal electron acceptors