ATP homeostasis

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ATP homeostasis. Energy systems homeostasis. ATP Common metabolic intermediate Powers muscular contraction Cell work Well-maintained over wide variations in energy turnover. Energy homeostasis. 3 basic energetic systems Immediate (ATP-PCr) Non-oxidative: anaerobic glycolysis - PowerPoint PPT Presentation

Text of ATP homeostasis

  • ATP homeostasis

  • Energy systems homeostasisATPCommon metabolic intermediatePowers muscular contractionCell workWell-maintained over wide variations in energy turnover

  • Energy homeostasis3 basic energetic systemsImmediate (ATP-PCr)Non-oxidative: anaerobic glycolysisOxidative: oxidative phosphorylation

  • Immediate energy systemsATP + actin + myosin Actomyosin + Pi + ADP + energyATP +H2O ADP + PiATP then resynthesized by Creatine kinase and adenylate kinase reactions in immediate energy systemsCa2+ATPase

  • Creatine kinase (CPK) is the enzyme that releases the energy stored in PCr to resynthesize ATPThe depiction at the R shows the creatine phosphate shuttleExceptionally small amounts of stored ATP and PCr (5-15s)These reactions occur in cytoplasm

  • Immediate energy systemsATP broken down to ADP and PiA buildup of ADP and Pi stimulate metabolismA buildup of ADP also inhibits the breakdown of ATPATP ADP + PiThus, Adenylate kinase reaction:ADP + ADP ATP + AMPUsed during very high energy turnover

  • Non-oxidative energy sources (continued)

  • Nonoxidative energy sourcesGlycogenolysis/glycolysisDepends on the start pointBreaks glucose (glycogen) down to pyruvatePyruvate then converted to lactateOccurs in cytoplasmImportance increases for events lasting longer than 15s and less than a couple of min.

  • Oxidative energy sourcesGlycolysispyruvate

  • Oxidative energy sourcesCan come from three primary sourcesCarbohydrate (glucose/glycogen)FatProteinSignificant stores of fatThus, the body will use mostly fat at rest

  • Complete oxidation of glucoseC6H12O6 + 6O2 6CO2 + 6H2O + 36 ATP

    Complete oxidation of palmitate (16C fatty acid)C16H32O2 + 23O2 16CO2 + 16H2O + 129 ATPAnd there are 3 fatty acids per molecule of fat (so, 387 ATP)

    Oxidation of amino acidsTricky and complicatedMust be deaminated or transaminated (NH2 group removed or converted to something else)ketoglutarateglutamateDeaminationTransamination

  • Capacity of the three energy systemsYou can see from table 3-5 the inverse relationship between the power of the 3 systems and their capacityImportantAll 3 energy systems are always being used to some extent, even at rest

  • Capacity vs Power

  • Athletic performanceNote the triphasic nature of the graphDifferent events may select out participants based on how they store energyNote similarity between genders immediateNon-oxidativeOxidative

  • Enzymatic regulation

  • Enzymatic regulationSubstrate: reactantActive site: where substrate attachesEnzyme-substrate complexConformationCan be changed by co-factors (modulators), which affect enzyme-substrate interaction and rate of reactionModulators (alter the Rx rate)Can increase reaction rate (stimulators)ADP, AMP, PiSlow reaction rate (inhibitors)ATP

  • Enzymes 2Modifaction by modulators called allosterism (bind to specific site and either inc/dec Rx rate)Common allosteric modulatorsAdd or remove Phosphate ion (Pi)Kinases and phosphatasesAlters rate of enzymatic reactionVmax: maximum rate of enzymatic reactionKM; Michaleis-Menton constant; substrate concentration that gives Vmax

  • Hexokinase: phosphorylates glucose in muscleGlucokinase: phosphates glucose in liver

  • Changes in energy stateNote that ATP is relatively well-maintainedPCr begins to get depleted during high intensity workADP, AMP, Pi change as would be expected from signals of intracellular energy demand

  • Chapter 4Basics of metabolism

  • Metabolism:Sum total of all chemical processes within an organism; produces heat. Why?Metabolic rate: can be measured as heat productionO2 consumption provides for almost all of our metabolic needs, so Vo2 provides a very good index of metabolic rateHigh Vo2 means high metabolic capacity

  • Energy transductionConversion of energy from one form to another3 major types of interconversionsPhotosynthesisCellular respirationCell workPhotosynthesis: plantsSunlight + 6 CO2 + 6 H2O C6H12O6 + 6O2Cellular respiration: non-plantsC6H12O6 + 6O2 6CO2 + 6 H2O + energyCell work (ATP used)Mechanical, synthetic, chemical, osmotic and electrical

  • Metabolism and heat production in animalsLiving animals give off heatMetabolism is functionally heat productionCalorie: heat required to raise 1 gram water 1 CKilocalorie: what is commonly referred to as a calorie

  • CalorimetryDirect calorimetryPlace entire animal in calorimeterMeasure heat productionIndirect calorimetryMeasure oxygen consumptionEasier

  • Indirect calorimetrySimple, measures Vo2 and Vco2Allows work to be performed while obtaining index of metabolic rateGives a good index of fitness

  • Steady stateNote how it takes a while for caloric output to stabilize during a certain workloadThis stable area is called steady stateTo calculate energy expenditure, steady state must be achieved

  • Concept of respiratory quotient/respiratory exchange ratioRatio of Co2 produced (Vco2) to O2 consumed (Vo2)If measured at the cellular levels: RQIf measured at the mouth: RERAlso RER can go above 1.0, RQ cannotWhy?Complete oxidation of glucoseC6H12O6 + 6O2 6CO2 + 6H2O + 36 ATP

    Complete oxidation of palmitate (16C fatty acid)C16H32O2 + 23O2 16CO2 + 16H2O + 129 ATP

  • Indirect calorimetryCouple reasonsWith pure glycolysis, RQ or Vco2/Vo2 is 1.0However, when measured at the lung (RER), additional Co2 production from acid buffering reactions must be factored inBuffering of lactic acidHLAH+ + La-H+ + HCO3- H2CO3H2CO3 H2O + CO2

  • C6H12O6 + 6O2 6H2O + 6CO2H+ + HCO3- H2CO3 H2O + CO2This extra CO2 is called non-metabolic CO2

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