Review Sheet for BIOC 460 at UA
Review Sheet for BIOC 460 at UA
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Date Created: 02/06/15
Dr Roger Miesfeld Bioc 460 Spring 2005 Bioenergetics and Metabolism 1 De ne the terms catabolism and anabolism 2 Why is anabolism favored under conditions of high Energy Charge in the cell 3 Name ve mechanisms of metabolic regulation in higher organisms 4 In 1783 Antoine Lavoisier used a crude calorimeter to demonstrate that the thermodynamic principles hold true in living systems What were the results of his experiment and what thermodynamic principle was con rmed 5 What is the Second Law of Thermodynamics and how does it apply to energy conversion systems in a living organism such as yourself 6 What is the difference between AG 39 and AG Write an equation that de nes AG 39 when a reaction is at equilibrium Why doesn39t this equation apply to most metabolic reactions in a living organism 7 Describe what happens to the metabolic flux of glucose before and after eating breakfast in terms of glycogen and pyruvate levels in liver cells and the two peptide hormones that control blood glucose levels 8 Glycolysis converts glucose to pyruvate by the following stoichiometry Glucose 2 ADP 2 Pi 2 NAD gt 2 Pyruvate 2 ATP 2 NADH 2 H 2 H20 Gluconeogenesis converts pyruvate to glucose by the following stoichiometry 2 Pyruvate 4 ATP 2 NADH 2H 4 H20 gt Glucose 4 ADP 4 Pi 2 NAD What is the net result ofthese two reactions and what does this tell us about role of enzyme regulation in glycolysis and gluconeogenesis Dr Roger Miesfeld Bioc 460 Spring 2005 Answers 1 Catabolism breakdown of macromolecules for the purpose ofATP generation Anabolism biosynthesis of macromolecules for the purpose of life this requires ATP 2 The energy charge ofthe cell refers to the relative concentrations of ATP ADP and AMP When the energy charge is high it means that ATP concentrations are high relative to AMP and ADP Anabolic pathways biosynthesis require ATP therefore a high energy charge in the cell favors anabolism 3 The ve mechanisms of metabolic regulation are Allosteric interactions Covalent modification Enzyme levels Compartmentation Metabolic specializations of organs FnPFDN 4 Lavoisier found that the amount of metabolic heat given off by the guinea pig was the same amount ofenergy that would come from oxidation of fuels through combustion This experiment con rmed the First Law of Thermodynamics that energy is neither created or destroyed but rather converted from one form to another 5 The Second Law of Thermodynamics states that all natural processes in the Universe tend toward disorder entropy in the absence of energy input Many types of biochemical reactions in living organisms are maintained at a steadystate that is far from equilibrium with the environment This is done by harnessing energy released from the Sun thermonuclear fusion reactions to generate chemical compounds such as ATP which is used in coupled reactions to restrain entropy as long as possible Photosynthetic organisms convert sunlight into chemical compounds such as carbohydrates which are then used as chemical fuel by nonphotosynthetic organisms 6 AG 39 refers to the standard free energy change ofa reaction under biochemical conditions when the reaction is allowed to go from 1M concentration ofall reactants and products to equilibrium The difference in free energy under these two conditions 1 M concentration and at equilibrium is expressed in units of kilojoules kJ or kilo Calories kcal AG is the actual free energy change in a reaction that is calculated from the known AG 39 value and the steadystate concentrations ofreactants and products in a living cell When a reaction is at equilibrium AG 0 and AG 39 is de ned by the equation AG AG RT In Bactual Aactual 0 AGO 39 RT 39 In Bequilibrium Aequilibrium This reaction does not apply to most metabolic reactions in a living organism because life requires that reactions do not reach equilibrium with the environment if they did the organism would be dead Dr Roger Miesfeld Bioc 460 Spring 2005 7 Before breakfast glucose levels are low in the blood due to a night of fasting presumably which triggers the release ofglucagon from the pancreas Glucagon receptors are activated in liver cells leading to an increase in glycogen degradation to produce free glucose as well as glucose synthesis from pyruvate gluconeogenesis Together these two metabolic pathways increase glucose export to maintain appropriate blood glucose levels for brain function 5 mM After breakfast blood glucose levels rise leading to insulin release from the pancreas and stimulation of insulin receptor signaling in liver cells Under these conditions the metabolic ux ofglucose is shifted toward glucose import and storage as glycogen and energy conversion from glucose to pyruvate to produce ATP glycolysis 8 Net reaction 2 ATP 2 H20 gt 2 ADP 2 Pi Enzyme regulation is critical in controlling these two opposing pathways otherwise ATP would be continually hydrolyzed leading to futile cycling and heat production Coordinate control of glycolytic and gluconeogenic enzymes shifts the metabolic ux in the appropriate direction in response to glucose availability to prevent futile cycling
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