CHEMISTRY · Multi-part · ISC · Chemistry · Chemical Thermodynamics · Some Basic Concepts of Chemistry
Problem
Inside a muscle cell, the conversion of metabolite X to metabolite Y is endergonic under standard-state conditions, with $
\Delta G^\circ = +12.0\,\text{kJ mol}^{-1}.Thecellhasatemporarystoreof1.50\,\text{mmol}$ of ATP that can be hydrolyzed directly to AMP and pyrophosphate:
$
\text{ATP} + \text{H}_2\text{O} \rightarrow \text{AMP} + \text{PPi}
\Delta G^\circ = -45.6\,\text{kJ mol}^{-1}
$
Assume that the pyrophosphate produced is immediately broken down in a separate reaction whose energetics do not need to be considered here.
(a) Calculate the maximum number of moles of metabolite Y that can be formed from metabolite X using the available ATP supply, assuming standard-state conditions and 100 % coupling efficiency.
(b) Metabolite Y has a molar mass of 174g mol−1. Determine the maximum mass (in grams) of metabolite Y that can be synthesized with the given ATP supply.
(c) Give one biochemical reason why the actual yield of metabolite Y in a real cell would be lower than the maximum calculated in part (b).