CHAPTER EIGHT INTRO TO METABOLISM Metabolism totality of an organism s chemical reactions Emergent property of life that arises from interactions between molecules within the orderly environment of the cell Metabolic pathway o STARTING MOLECULE ENZYME 1 ENZYME 2 ENZYME 3 o STARTING MOLECULE REACTION 1 REACTION 2 REACTION 3 PRODUCT PRODUCT Similar to red yellow and green stoplights that control the flow of car traffic enzymes regulate metabolic supply demand Metabolism manages the material and energy resources of the cell Some metabolic pathways release energy by breaking down complex molecules to Like a highway Regulated Interactive pathways simpler compounds o catabolic pathways respiration o Cellular respiration o Biosynthetic pathways o Synthesis of amino acid Anabolic pathways consume energy to build complicated molecules from simpler ones Bioenergetics study of how energy flows through living organisms ENERGY The capacity to cause change o Kinetic energy energy of motion Depends on mass and velocity o Potential energy energy of rest Depends on mass o Thermal energy energy of random moving particles heat o Chemical energy potential energy available for release in a chemical reaction Work transferring energy The study of the energy transformations that occur in a collection of matter o System matter under study Isolated system unable to exchange either or matter with its surroundings Open system energy and matter can be transferred between the system and its surroundings o Surroundings everything outside the system First law of thermodynamics o Energy of the universe is constant o Energy can be transferred and transformed but it cannot be created nor destroyed o Principle of conservation of energy Second law of thermodynamics o Every energy transfer or transformation increases the entropy of the universe Entropy a measure of disorder or randomness Doesn t do anything it is a result For a process to occur spontaneously it must increase the entropy of the universe Living systems increase the entropy of their surroundings as predicted by thermodynamic law An organism takes in organized forms of matter and energy from the surroundings and replaces them with less ordered forms Energy can be used to increase order in the system o YOU NEED ENERGY TO CREATE ORDER o Energy is always increasing o Energy is made available to do work as order decreases in the system Energy creates bonds and links atoms together Entropy cannot do any work Free energy o Can go up or down absorbing or extracting energy o The portion of a system s energy that can perform work when temperature and pressure are uniform throughout the system o G H T S o Energy available to a cell to do work Gibbs free energy G Available to do work Useable energy Greaction Gproducts Greactants G pos or neg POS more free energy to store endergonic o Input of energy required NEG less free energy energy comes out exergonic o Output of energy required total energy enthalpy o G H TS TS unusable energy temperature entropy o Enthalpy energy stored in chemical bonds Chemical equilibrium o Chemical reactions are reversible Activation energy o Free energy of activation o Energy required before a chemical reaction will start ENZYMES Enzymes lower activation energy Enzymes do not o Affect Keq o Affect delta G o Enzymes speed up the reaction o Do not change the thermodynamics Enerzyme catalysts End with ase Mostly protein Reactacts substrates Enzyme unchanged re usable Interaction at active site Properties of enzymes o Specificity each enzyme has a job to do Due to shape Active site and induced fit Activity of enzymes depend on induced fit Ph Temperature Co factors o Metal ions Inhibitors o Competitive The function of enzymes depends on the active site shape and Binds to active site o Noncompetitive Distorts shape Binds everywhere except active site o You can regulate any enzyme in a chain It depends on the natural of the pathway Control of enzymes o Allosteric control Allosteric site is where effector molecules bind Binding of effector molecule changes the conformation of the enzyme Effector can be Activator Inhibitor CHAPTER NINE CELLULAR RESPIRATION Fundamentals of metabolism Glucose metabolism Glucose is the starting point for cellular respiration o Cellular energy ATP adenosine triphosphate 3 phosphate groups makes molecules unstable o ATP ADP Pi Delta G 7 3 kcal mole unstable It does take energy to break the phosphate bonds in ATP but not a lot o Because phosphate has Oxygen very electronegative It s like compressing a spring to store energy by the bonds that are trying to push apart o The bonds are ready to snap By adding phosphate groups the negative O s repel each other it s under a lot of stress O s shove each other away bonds are getting stressed The energy released from hydrolysis of ATP is coupled with a second endergonic reaction o Store energy in bonds o Need energy to do work o Coupling reactions Putting 2 reactions together Can use up energy or happen spontaneously By adding a phosphate to a reaction you add energy and make it unstable reactive Neg delta G spontaneous reactions ADP ATP cycle o Energy from catabolism exergonic energy releasing processes o Energy for celluluar work endergonic energy consuming processes o 3 ways to make ATP from ADP Substrate level phosphorylation No oxygen required Typical enzyme mediated process Take a molecule of phosphate from one substance and add it to another substance Anaerobic o Life Without Oxygen Diversity in cellular respiration Find electron acceptors Oxygen aerobic respiration Inorganic molecule nitrate etc anaerobic respiration Organic molecule pyruvate etc fermentation o Anaerobic respiration Many prokaryotes use alternative final electron acceptors Methanogens o CO2 is reduced to CH4 Sulfur bacteria o SO4 is reduced to H2S Using a different electron transport not oxygen o Energy released when covalent bonds are broken is coupled with the remaking of ATP from ADP and Pi Ex PEP pyruvate take phosphate from PEP and put it on ADP Oxidative phosphorylation Requires oxygen Respiration Uses membrane proteins in mitochondria Use the transfers of electrons o Oxidation reduction reactions o They are correlated o Electrons get less and less energy Redox reactions o Transfer of hydrogen atoms not ions between two molecules is a redox reaction Transfer includes the hydrogen atom s electron o Molecule that accepts a hydrogen electron is reduced o Molecule that loses a hydrogen electron is
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