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• • • Microbial Metabolism What is metabolism? All chemical reactions/activities in cell – Catabolism • • Hydrolysis Use energy to make ATP – – Anabolism • • Dehydration synthesis Need energy for reaction – • • • • • • ADP + Pi + energy ATP ATP ADP + Pi + energy Enzymes frequently catalyze reactions Oxidation/reduction What is the difference between… Hydrolysis Condensation (dehydration synthesis) Exergonic vs. endergonic • What are enzymes? • Without enzymes, collision theory rules – – • Need sufficient activation energy Number of molecules above this activation level = reaction rate Enzymes are molecules that lower the ______________ – – Catalysts Work on substrate… • • What does the enzyme work on? Substrate – • Enzyme-substrate complex forms temporarily – – – • • • Lock and key model Highly specific fit End in -ase Turnover number – – • Molecules which are changed during reaction Number of molecules enzyme converts per second DNA polymerase = 15; lactate dehydrogenase = 1,000 What are the parts of an enzyme? Some are only a polypeptide chain Most have two parts – – – Apoenzyme (polypeptide chain) Cofactor (inorganic) or coenzyme (organic) • • NAD+ (nicotinamide adenine dinucleotide) us. catabolic • • Coenzyme A (CoA)—pantothenic derivitive (another B vitamin) NADP+ (nicotinamide adenine dinucleotide phosphate) anabolic Others are metals: Cu, Mg, Mn, Zn, Ca, Co Together these form holoenzyme • How does an enzyme work? • Enzymes controlled by – Enzyme synthesis • • How much is made Hormones can influence (e.g. TH) us. – Enzyme activity • Temperature influences – • • pH influences Substrate concentration influences – • • Saturation point How does an enzyme work? Inhibitors influence – Competitive • – Fill active site: sulfanilamide vs para-aminobenzoic acid (PABA) Non-competitive • • • • • • • • • • Denaturation Allosteric inhibition Factors Influencing Enzyme Activity Enzymes can be denatured by temperature and pH Factors Influencing Enzyme Activity Temperature pH Substrate concentration Factors Influencing Enzyme Activity Competitive inhibition Factors influencing enzyme activity • • • • • • • • • • • Feedback inhibition Cell Energetics Oxidation-Reduction Oxidation is the removal of electrons. Reduction is the gain of electrons. Redox reaction is an oxidation reaction paired with a reduction reaction. Oxidation-Reduction In biological systems, the electrons are often associated with hydrogen atoms. Biological oxidations are often dehydrogenations. What happens in carbohydrate catabolism? Glucose usually is substrate Glycolysis – • 2 ATP Followed by either – Aerobic respiration • ___ ATP – Anaerobic fermentation • No more ATP • What is ATP? • • • • • • • Adenosine triphosphate Made by phosphorylating ______ Equation: What is glycolysis? First step to making TP from glucose Convert glucose to _____________ Some bacteria can breakdown other molecules – Pentose phosphate pathway (pentoses) • E. coli, Bacillus subtilis • • • • • • • • What happens next? If oxygen present Preparatory Stage Two ATPs are used Glucose is split to form two Glucose-3-phosphate Energy-Conserving Stage Two Glucose-3-phosphate oxidized to two Pyruvic acid • • • • • • Four ATP produced Two NADH produced Intermediate Step Pyruvic acid (from glycolysis) is oxidized and decarboyxlated. What is the Krebs Cycle? AKA citric acid cycle – Acetyl CoA (2 carbons) releases energy – Produces ATP, CO2, NADH, FADH2 • NADH and FADH2 to Electron transport chain (ETC) • What are some intermediates in the Krebs cycle? • • • • • • • • • • Some drugs are metabolized similar to these: citric acid (6 carbons) iso-citric acid (6) alpha-ketoglutaric acid (5) succinyl CoA (4) succinic acid (4) fumaric acid (4) malic acid (4) oxaloacetic acid (4) Krebs cycle animation • What is the electron transport chain? • Carrier molecules facilitate oxidation and reduction – Oxidation: loss of electron – Reduction: gain of electron • Transfer electrons from higher to lower energy compounds – Chemiosmosis w/ oxidative phosphorylation • • • Prokaryotes: PM • • First ETC animation Eukaryotes: mitochondrial crista Disruption of ETC leads to death! – Cyanide Second ETC animation • What is the sum reaction for aerobic respiration? Glucose + 6 H2O + 38 ADP + 38 Pi 6 CO2 + 6 H2O + 38 ATP • What happens in anaerobic respiration? • Final electron acceptor is not oxygen – – – – Various amounts of ATP produced Slower and less ATP than aerobic respiration Uses some parts of Krebs cycle Thus slower growth for anaerobes than aerobes • What is fermentation? • Pyruvic acid from glycolysis – – – Converted to end-products If bacteria only produce lactic acid = homolactic No additional ATP • • • What is alcohol fermentation? Also happens after glycolysis Produces ethanol and CO2 • Heterolactic: produces lactic acid + other acids, alcohols • What happens in lipid & protein catabolism? • • Some bacteria don’t like carbs! Lipases break down ______ – – • Useful for oil spill clean up Extracellular proteases & peptidases break down _______ – • • • Krebs cycle oxidizes products Deamination converts amino acids to usable form for Krebs cycle • By production is ammonia Anaerobic Respiration Energy produced from complete oxidation of one glucose using aerobic respiration. ATP produced from complete oxidation of one glucose using aerobic respiration.