25mm adp025mm pi 165mm mass ac0on ra0o q 18104

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Unformatted text preview: – Adenosine Diphosphate •  AMP – Adenosine Monophosphate ATP hydrolysis reac0on •  Thermodynamically unstable, ΔG < 0 –  Equilibrium lies far toward hydrolysis. •  Kine0cally stable –  In absence of a catalyst, breakdown is very slow –  Useful characteris0cs for energy “currency” of cells Why the large nega0ve ΔG’o? ATP ΔG ADP+Pi What stabilizes ADP + Pi rela0ve to ATP? 4. More moleculeshigher entropy Magnesium affects ATP free energy •  Mg2+ in the cytosol binds to ATP and ADP •  True substrate is MgATP2 ­ •  Actual free energy of ATP hydrolysis under intracellular condi0ons can vary from cell to cell, 0me to 0me  ­log10[Mg2+] From Berg..Stryer, 5th ed. p. 394 Actual free energy of ATP hydrolysis •  In living cells, concentra0ons of substrates are far from standard condi0on (1.0 M) –  actual free energy is very different from ΔG’°=−30.5 kJ/mol –  concentra0on is regulated to keep ATP’s potency •  In human, [ATP]≈2.25mM, [ADP]≈0.25mM, [Pi] ≈1.65mM mass ac0on ra0o Q = 1.8×10–4 << 1. What is actual free energy under these condi0ons? [ ADP][Pi ] [ ATP] = $30.5 kJ/mol + "Gp = "...
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