Intracellular Compartmentation and Metabolism

There are many interconnections between the main metabolic pathways. Many substrates and regulatory molecules, and some enzymes, are common to several pathways. An understanding of these interconnections requires knowledge of (1) the subcellular locations and concentrations of the enzymes involved, (2) the concentrations of metabolites within different subcellular organelles, and (3) the nature of permeability barriers for metabolites between the organelles these barriers divide the cell into a number or compartments for each metabolite. 

Lactate dehydrogenase is a cytosolic enzyme that is present at high enough concentrations for its reaction to be at equilibrium in many cells. 

The equilibrium constant for this reaction is known from in vitro studies. How could this be used to calculate the cytosolic NADH/NAD+ ratio  

The cytosolic concentrations of pyruvate and lactate can be obtained from the results of freeze-clamping experiments. Hence, from the known [H + ] of the cytosol and the known equilibrium constant (Ke) 

A sample of acetic acid (1 mol) was completely oxidized to C02 and H20 in a constant volume adiabatic calorimeter, at 298 K. The heat released in the oxidation was 874 kJ. Calculate AH for the oxidation of acetic acid. 

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