(Microsoft PowerPoint - ATP angl.ppt [Re\236im kompatibility])

The role of ATP in metabolismMUDr. Martin Vejražka, PhD.This slideshow is available on-linewww.lf1.cuni.cz, link „e-learning“el.lf1.cuni.cz

Adenosin triphosphate (ATP)NH 2- O OPNN- O- OPOONONOOPOO -HOOH

ATP, ADP, AMP a cAMP Macroergic compound Role in signaling– cAMP– AMP Binds transitive metals RNA

What is macroergic bond???… back to thermodynamics

Thermodynamics Two axioms Abstract quantities (entropy, enthalpy…) Idealised processes and stuffs (reversibleaction, universal gas…) Is not interested in inner structure ofmateria Does not deal with time, rate of processes „Simple“ and „easy to understand“system

Thermodynamic functionsU inner energyH enthalpy = heat contentS entropy = measure of randomnessF free energyG free enthalpyCannot be measured absolutely, changes are quantifiedStandard quantities (G 0 , S 0 …) defined forcertain „standard state“

Enthalpy Constant volume:∆U U = Q∆ inner energy = reaction heat Constant pressure∆H H = Q– a part of energy corresponds tomechanical work

Enthalpy ∆H H … heat exchanged between the systemand its surrounding H … heat content – how much heat can bemaximally produced by the system If volume is not changed: equal to changein inner energy

Free enthalpy A portion of enthalpy can be used toincrease arrangement of the system∆G G = ∆H – T·∆S

Free enthalpyinclinationto react=decreasein energyof system+increase inrandomness ofsystem∆G G < 0 … reaction runs spontaneously∆G G = 0 … equilibrium∆G G > 0 … need for energy

Free enthalpy∆G G = ∆G 0 ‘ +RT·ln[products]/[reactants]∆G 0 … all concentrations 1 mol/l∆G 0 ‘ … + aquaeous sol., pH = 7,0∆G 0 = - RT·ln K‘

Course of reaction∆G G = ∆G 0 ‘ + RT·ln[products]/[reactants]Can run?∆G G < 0Real concentration ofcompoundsProperties of reactionK

Course of reaction∆G G = ∆G 0 ‘ + RT·ln[products]/[reactants]CouplingofreactionsTaking products awayIncreasing reactant concentration

… back to ATP …

ATP Hydrolysis of ATP is stronglyexergonicATP → ADP + P i ∆G 0 ‘ = -30,5 kJ/molThermodynamics: reaction may run spontaneouslyKinetics: reaction does NOT run spontaneously

Hydrolysis of ATPwithout enzymewith enzyme∆G0‘ = -30,5 kJ/mol

Coupling of reactionsheatModified from Murray et al.: Harper‘s Biochemistry

Coupling of reactionsATPheatADPADP

Irreversible reactions

Irreversible reactions

How to make ATPoxidation of fuelsmitochondriarespiratory chainproton gradient is formedreducing equivalentsNADH, FADH 2phosphorylation of ADP= formation of ATP

Other macroeric compoundsPhosphoenolpyruvateCarbamoylphosphateBisphosphoglycerateCreatinphosphateATPADPPyrophosphatePhosphorylated carbohydratesOther:thioesters (including acetylcoenzyme A)esters of aminoacidsS-adenosylmethioninphosphoribosyl pyrophosphate…

Other properties of ATP A complex with Mg 2+ works– Mg is cofactor of all enzyme-catalysedreactions of ATP

Some reactions of ATP Adenylate kinaseATP + AMP ↔ 2 ADP Nucleoside kinasesATP + GDP ↔ ADP + GTP