Reaction #8 in the citric acid cycle is shown below. The Gº\' for this reaction
ID: 67248 • Letter: R
Question
Reaction #8 in the citric acid cycle is shown below. The Gº' for this reaction is +29.7 kJ/mol. This is a significantly endergonic reaction so how is it possible that this reaction occurs in the cell?
malate + NAD+ oxaloacetate + NADH + H+
a)The concentration of oxaloacetate in the cell is extremely low.
b)The concentration of malate in the cell is extremely low.
c)Both of these strategies would allow the reaction to occur in the cell.
d)Neither of these strategies would allow the reaction to occur in the cell.
Explanation / Answer
a)The concentration of oxaloacetate in the cell is extremely low.
The 8th step in citric acid cycle (malate + NAD+ oxaloacetate + NADH + H+) is highly exergonic, and the oxaloacetate formed during this reaction is continuously removed out, which maintains the extreme low concentrations of oxaloacetate. in the cell. This favors the malate dehydrogenase reaction to proceed and form oxaloacetate.
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