NU BIOL 1121 - PRINCIPLES OF METABOLISM

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METABOLISM: FEULING CELL GROWTHPRINCIPLES OF METABOLISM- Two componentso Exchange Reactions: convert one molecule to anothero 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 theproducts Most energy lost in the form of heato 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 productsHarvesting 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- Available to do work, energy released when bond broken- Components of the Metabolic Pathway o Intricate and finely tuned processeso A series of intermediate compounds are formed before the end product is reached o Can be linear, branched, of cylindrical and modulated at certain pointso 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 mechanismso The Role of ATP ATP- Energy currency of the body- Immediate donor of free energy  ADP- 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 formationof 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 oxidizedo The molecule that is the proton acceptor is reduced- In biological terms…o The removal of hydrogen atom is typicallyoxidationo The addition of hydrogen is reductiono Dehydrogenation: an oxidation reaction in whichan electron and an accompanying proton areremovedo Hydrogenation: a reduction reaction in which anelectron and accompanying proton is addedo Hydrogen carrier: if a proton accompanies anelectron The Role of Electron Carriers- Designated molecules ascarriers 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 energyo 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 pathwayso 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 Metabolismo Central metabolic pathways: three key metabolic pathways are used to gradually oxidize glucose completely to CO2 Glycolysis (Embden-Meyerhof-Parnas)- 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 Pentose Phophaste Pathway- Breaks down glucose, but primary use is production of compounds usedin 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) Krebso 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. Phosphorylationo FADH2 and NADH transfer electrons to the e. transport chain, which ejects protons from the cell to generate proton motive forceo Also serves to recycle the carriers after they deposit their e-- Aerobic Oxygen as final receptor anaerobicother receptor and Krebso 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 Actiono Enzymes have an active site that a substrate binds to by weak forces, called an induced fit, and creates an enzyme-substrate complexo Simple or conjugated enzymeso 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


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NU BIOL 1121 - PRINCIPLES OF METABOLISM

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