METABOLISM FEULING CELL GROWTH PRINCIPLES OF METABOLISM Two components o Exchange Reactions convert one molecule to another o Catabolism harvests energy released during the breakdown of compounds such as glucose using that energy to synthesize ATP release energy Exergonic Reactants the starting compounds have more free energy that the products Most energy lost in the form of heat o Anabolism biosynthesis utilize energy stored in ATP to synthesize and assemble proteins and things that make up the cell Captures energy into high energy bonds like in PEP ATP and GTP Endergonic Reactants have less free energy than the products Harvesting Energy Energy the capacity to do work Potential and kinetic forms and can be stored in various forms Cannot be created or destroyed Photosynthetic organisms that harvest energy from sunlight Convert the kinetic energy of photons into the potential energy in chemical bonds Chemoorganotrophs obtain energy by degrading organic compounds such as glucose releasing the energy of their chemical bonds Thus most depend on energy generated by autotrophs Free energy the energy that can be harvested by breaking down a compound Components of the Metabolic Pathway Available to do work energy released when bond broken Intricate and finely tuned processes o o A series of intermediate compounds are formed before the end product is reached o Can be linear branched of cylindrical and modulated at certain points o The Role of enzymes Facilitate steps of metabolic pathways Can aid in accelerating a substrate into the product Lowers the activation energy 3D shape from amino acid sequence DNA structural genes Do not become substrates or products Not used up needed in small numbers Very specific lock and key mechanisms o The Role of ATP ATP ADP Energy currency of the body Immediate donor of free energy Electron and free energy receptor Adding a phosphate group adds energy High energy phosphate bonds are formed due to the negative charges that repel each other Substrate level phosphorylation Uses chemical energy to form ATP from ADP and Pi Used directly in metabolic processes Oxidative phosphorylation Harvests the energy of the proton motive force to do the same things Electron chain proton motive force Photophosphorylation Utilized by autotrophs use the energy of the sun to drive the formation of the proton motive force electrochemical gradient established as protons are expelled from the cell o The Role of the Chemical Energy Source Energy source compound broken down be cell to release energy Can be organic and nonorganic sources Oxidation Reduction Reactions One or more electrons are transferred from 1 molecule to another o The molecule that is the proton donor is oxidized o The molecule that is the proton acceptor is reduced In biological terms o The removal of hydrogen atom is typically oxidation o The addition of hydrogen is reduction o Dehydrogenation an oxidation reaction in which an electron and an accompanying proton are removed o Hydrogenation a reduction reaction in which an electron and accompanying proton is added o Hydrogen carrier if a proton accompanies an electron The Role of Electron Carriers Designated molecules as carriers of e Made from vitamins o Niacin NAD NADP o Riboflavin FAD NAD FAD NADP reduced forms NADH FADH2 used for oxidative phosphorylation electron transport to make ATP NADPH reducing power for biosynthesis rxns considered hydrogen carriers because along with electrons they carry protons reduced electron carriers NADH etc represent reducing power because their bonds represent a usable form of energy o used to generate the proton motive force ultimately they are transferred to a molecule such as oxygen that is called a terminal electron receptor Percursor metabolites Metabolic intermediates produced at specific steps in catabolic pathways that can be used in anabolic pathways o Anabolism serve as raw material used to make subunits of macromolecules An efficient organism like E coli can make all materials from a small amount of precursors Overview of Metabolism o Central metabolic pathways three key metabolic pathways are used to gradually oxidize glucose completely to CO2 Glycolysis Embden Meyerhof Parnas Pentose Phophaste Pathway Most common pathway to initiate the breakdown of glucose Gradually oxidizes the 6 carbon sugar glucose 2 molecules of pyruvate 3 carbon small amount of ATP and reducing power in the form of NADH Bacteria use a different pathwat Entner Doudoroff pathway to do the same thing but with different enzymes Breaks down glucose but primary use is production of compounds used in biosynthesis precursors and NADPH Most directed out the cycle for use in biosynthesis but 1 is used to oxidize and create ATP Any pyruvate generated most be broken into a 2 carbon derivative accomplished in the transition step o In this step CO2 is removed reducing power is generated and acetyl CoA is formed by joining the resulting particles Tricarboxylic acid TCA cycle Krebs o The acetyl CoA enters the Kreb s cycle which initiates oxidizations and the release of 2CO2 Respiration uses the reducing power in glycolysis the transition step and the TCA cycle to generate ATP via ox Phosphorylation o FADH2 and NADH transfer electrons to the e transport chain which ejects protons from the cell to generate proton motive force o Also serves to recycle the carriers after they deposit their e Aerobic Oxygen as final receptor anaerobic other receptor and Krebs o Amphibolic the dual nature of the metabolic pathways Provide cell with energy via ATP reducing power and precursor metabolites Catabolic but metabolites and reducing power can be utilized in biosynthesis Mechanisms and Consequences of Enzyme Action o Enzymes have an active site that a substrate binds to by weak forces called an induced fit and creates an enzyme substrate complex o Simple or conjugated enzymes o Have a narrow range increases speed of reaction up to a point where it is denatured most work best in low salt and neutral pH ex thermophiles o Regulated in order to prevent expenditure of cell components energy and overproduction Amount and activity regulated Constitutive enzymes always present high levels more substrate does not increase enzyme much ex enzymes of central metabolism like Glycolysis enzymes absent when not needed usually tiny amounts Inducible enzymes made when needed Cofactors and Conenzymes ex beta galactosidase prevents waste of energy by cell o Cofactor a non protein