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Energetics in Biochemistry – ATP (10.1-10.3)

Energetics in Biochemistry – ATP (10.1-10.3). Adenosine triphosphate ( ATP ) is used to generate energy to insure certain biological processes proceed spontaneously

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Energetics in Biochemistry – ATP (10.1-10.3)

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  1. Energetics in Biochemistry – ATP (10.1-10.3) • Adenosine triphosphate (ATP) is used to generate energy to insure certain biological processes proceed spontaneously • Hydrolysis of ATP to form adenosine diphosphate (ADP) is exergonic (energy is released) by about 30 kJ/mol in the biochemical standard state • ATP is reformed from ADP through phosphorylation (during glycolysis) • Many biochemical processes are coupled to the hydrolysis of ATP because by themselves they are endergonic (energy must be absorbed) • Phosphorylated intermediates are generated when ATP is used • Principle of common intermediates requires the intermediate to be utilized in one of the following steps (essentially just Hess’s law) • Since phosphorylated species are generated and hydrolyzed in these ATP/ADP coupled reactions, it is important to know which species are the most effective phosphate donors • Phosphate transfer potentials are used to determine which species are the most effective phosphate donors (value is negative of Gibbs energy of hydrolysis) • Whichever intermediate has the higher PTP is the better phosphate donor

  2. Energetics in Biochemistry – Glycolysis (11.1-11.2) • Glycolysis is the process of breaking down glucose to form 2 pyruvate molecules • Pyruvate is used in the Krebs cycle to form reducing agents (e.g., NADH) used in the electron transport chain • Some ATP is also synthesized during glycolysis • Formation of some intermediates in the glycolytic pathway are endergonic under standard biochemical conditions • ATP hydrolysis can be used to make formation of these intermediates exergonic (e.g., phosphorylation of glucose – step 1) • Cellular conditions are not standard, so the actual Gibbs energy changes are exergonic (or nearly exergonic) under these conditions • Formation of ATP occurs in two steps, where the PTP of the intermediates is greater than that of ATP • Steps that form ATP require energy to be put into the synthesis of ATP from ADP

  3. ATP

  4. Phosphate Transfer Potentials

  5. Glycolysis – Steps 1-5

  6. Glycolysis – Steps 6-10

  7. Glycolysis Under Standard and Cellular Conditions

  8. PTP of Glycolytic Intermediates

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