Under standard biochemical conditions ( , , )

CHEMISTRY · Multi-part · AP · Chemistry · Thermodynamics and Electrochemistry · Thermodynamics and Electrochemistry

Problem

Under standard biochemical conditions (25 ∘ ⁣C25\,^{\circ}\!\text{C}, 1 bar1\,\text{bar}, pH=7pH=7), a chemist must drive the otherwise unfavorable dehydration of 2-phosphoglycerate to phosphoenolpyruvate (PEP). The dehydration step alone has ΔG∘=+10 kJ mol−1\Delta G^{\circ}=+10\,\text{kJ mol}^{-1}. Table 3 lists three hydrolysis reactions available in the same compartment. Table 3 Potential Hydrolysis Reactions
ReactionΔG∘ (kJ mol−1)\Delta G^{\circ}\,(\text{kJ mol}^{-1})
(1) ATP4−^{4-} → ADP3−^{3-} + Pi2−_\text{i}^{2-}−30
(2) NTP4−^{4-} → NDP3−^{3-} + Pi2−_\text{i}^{2-}−28
(3) acetyl phosphate → acetate−^{-} + Pi2−_\text{i}^{2-}−43
Assuming that each candidate hydrolysis could be enzymatically coupled to the dehydration step through a common phosphate-containing intermediate, (a) Calculation of overall ΔG∘\Delta G^{\circ} for each coupling (b) Selection of optimal hydrolysis reaction with reasoning

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