MICRB 106 1st Edition Exam 3 Study Guide Chapter 13 Metabolism What is metabolism How is ATP synthesized How is carbon utilized in microorganisms How does respiration and the electrons transport sytem work How are non glucose carbon sources metabolized Understand phototrophy and photosynthesis Understand nitrogen and sulfur metabolism and the biosynthesis of cellular components Metabolism Metabolism is the biochemical reactions happening in a living cell including catabolism anabolism and is mediated by enzymes Catabolism is the breaking gown of larger molecules to release energy and smaller precursors Anabolism is the use of smaller precursor molecules and energy in the form of ATP to build larger molecules Enzymes help catalyze biochemical reactions in a cell by binding to specific substrates and altering the molecules shape to complete a reaction quicker and easier Cofactors help enzymes put everything together Coenzymes are organic molecules Energy Chemical reactions can be performed when products have a lower free energy than the reactants because energy flows downhill Gibbs free energy G is energy released The change in free energy in a reaction is Go Exergonic reactions yield or give off energy resulting in a negative Go Endergonic reactions absorb energy resulting in a positive Go Activation energy EA determines the rate a reaction will occur ATP is the energy currency of the cell It is the most used form of chemical energy in a cell Catabolic reactions obtains ATP and anabolic reactions uses it up ATP synthesis Cells produce ATP using three different pathways Substrate level phosphorylation photophosphorylation and oxidative phosphorylation Substrate level phosphorylation is the transfer of a phosphate group to ADP from an intermediate molecule Often used in glycolysis Glycolysis is the catabolic breakdown of glucose into two 3 carbon pyruvate molecules This process uses two ATP molecules to get four ATP molecules Enzyme pyruvate transfers phosphate from phosphoenolpyruvate PEP intermediate to ATP Binding fructose1 6 biphosphate changes conformation lowers the E A binds PEP and ADP Photophosphorylation produces ATP using a proton gradient and electron transport system This pathway requires light energy and is used by photorophic cells Oxidative phosphorylation consists of electrons passing through an electron transport system which produces a proton gradient The flow of protons is used to drive ATP synthase to produce ATP from ADP Oxidation reactions result in losing an electron Reduction reactions result in gaining an electron Redox potential E is the tendency of a molecule to acquire electrons Reduction and oxidation redox reactions generate electron carriers Metabolic Groups of Microbes Microbes are grouped based off how they obtain Energy Chemotrophs and Autotrophs Electrons Organotrophs and Lithotrophs Carbon Heterotrophs and Autotrophs Carbon Utilization in Microorganisms Glycolysis consists of three different pathways that all generate energy and precursor molecules for metabolic pathways The Embden Meyerhof Parnas EMP has two phases the 6 carbon phase and 3carbon phase This pathway produces ATP and small precursor molecules and is used in all three domains eukaryote archea and bacteria The Entner Duodoroff pathway is useful for catabolism of carbohydrates that can not be processed by EMP This pathway does not produce as much ATP as the EMP pathway Moves sugars through a 6 carbon intermediate KDPG and is found in several aerobic and anaerobic bacterial species The Pentose phosphate pathway produces carbon precursors for other pathways NADPH electron carriers and is found in microbial organisms Fermentation uses organic molecules to get rid of the electrons carried by NADH Lactic acid fermentation is carried out by Gram positive microbes called lactic acid bacteria LAB Some examples of LAB s are pathogens flora of intestines and genitourinary tract and microbes used to make yogurt and sour cream Alcoholic fermentation is carried out by yeast and some bacteria Produces large amounts of ethanol and CO2 Used to produce beer and wine Mixed acid fermentation produced by different bacteria and fungi and used to produce acetone and butanol ATP regulates the enzyme phosphofructokinase in order to control the rate of fermentation Respiration is an alternative to fermentation which recycles NADH back to NAD The tricarboxylic acid TCA cycle pushes NADH through respiration The TCA cycle produces many electron carriers and carbon precursors but does not produce any ATP directly Feedback inhibition slows the enzymes of the cycle as NADH and ATP stores grow which regulates the TCA cycle Respiration takes electrons from the carriers Those electrons create a proton gradient as they pass through the electron transport system They are then passed on to terminal electron acceptors such as oxygen in aerobic respiration and other electron acceptors used in anaerobic respiration The Electron Transport System Aerobic respiration uses components embedded in membranes mitochondrial membranes in eukarya and plasma membranes in bacteria and archaea Electrons are passed down produce proton gradient and combine with oxygen and protons to produce water as a byproduct Anaerobic respiration is less efficient than aerobic respiration It does not use oxygen as the electron transport acceptor but uses sulfates and nitrates instead A proton motive force PMF is generated when electron carriers bring electrons to the electron transport system The PMF is the difference in potential energy across the cell membrane from protons being pumped out of the membrane during the electron transport system This causes a difference in proton concentration and charge which wants to become equalized across the cell membrane This results in ATP produced spin flagella and nutrient transport ATP synthase is the enzyme used to produce ATP As protons move through ATP synthase gamma subunit is used to rotate changing active site conformation which facilitates the addiotn of Pi to ADP to form ATP Chemolithotrophy uses reduced inorganic compounds for energy and electrons Due to membrane bound enzymes that remove electrons directly electron carriers are not required Metabolism of non glucose carbon sources Polysaccharides provide structural components of cell walls but are too large to be transported across the plasma membrane Polymers are enzymes used to break down polysaccharides into smaller subunits which can then enter