When pyruvate is the substrate for gluconeogenesis, which of the following is the fate of oxaloacetate prior to traversing the mitochondrial membrane?
A) conversion to phosphoenolpyruvate
B) oxidation to malate
C) reduction to malate
D) transamination to aspartate
E) transamination to glutamate

Question

Quizplus · Accepted Answer

Oxaloacetate is reduced to malate in the mitochondria to be transported across the mitochondrial membrane, as there is no direct transporter for oxaloacetate. Once in the cytosol, malate is oxidized back to oxaloacetate for gluconeogenesis. The inner mitochondrial membrane is impermeable to oxaloacetate (OAA). In order for the carbon atoms of OAA to be transported out into the cytosol, where they can serve as precursors for glucose synthesis, OAA is reduced to malate. The malate is transported across the inner mitochondrial membrane where in the cytosol is oxidized to OAA.

When Pyruvate Is the Substrate for Gluconeogenesis, Which of the Following