A researcher is attempting to couple the endergonic synthesis of malate from…

CHEMISTRY · Multi-part · A Level · Chemistry · Thermodynamics · Thermodynamics

Problem

A researcher is attempting to couple the endergonic synthesis of malate from oxaloacetate (

\Delta G^{\circ}=+29\,\text{kJ mol}^{-1}

) to one of several non-redox driving reactions available inside mitochondria. Table 2 summarizes the candidate reactions. Table 2 Mitochondrial Driving Reactions (non-redox only)

Label	Reaction	$\Delta G^{\circ}\,(\text{kJ mol}^{-1})$
A	GTP $^{4-}$ → GDP $^{3-}$ + P $_\text{i}^{2-}$	−31
B	ATP $^{4-}$ → AMP $^{2-}$ + PP $_\text{i}^{3-}$	−46
C	acetyl-CoA → CoA + acetate $^{-}$	−35

The laboratory has reported that pyrophosphate (PP

_\text{i}^{3-}

) is rapidly hydrolyzed to two inorganic phosphate ions with

\Delta G^{\circ}=−19\,\text{kJ mol}^{-1}

, and that this hydrolysis occurs virtually to completion. (a) Conceptual explanation of the redox restriction (b) Construction of reaction sequences and

\Delta G^{\circ}_{\text{net}}

calculations (c) Qualitative effect of PP

_\text{i}

hydrolysis on equilibrium (d) Final recommendation with justification

Related theory

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