When cells acquire sufficient energy such that the rate of flux through the TCA cycle declines, excess acetyl-CoA that cannot be oxidized is predominantly converted into fat. In order for the carbons in mitochondrial acetyl-CoA to serve as a precursor for fat synthesis, they must be delivered to the cytosol. Which of the following represents the molecule used to transport acetyl-CoA to the cytosol?
A) acetyl-CoA
B) carnitine
C) citrate
D) β-Hydroxybutyrate
E) pyruvate

Question

Quizplus · Accepted Answer

Citrate is the molecule that transports acetyl-CoA from the mitochondria to the cytosol for fatty acid synthesis.  Acetyl-CoA cannot freely diffuse across the membranes of the mitochondria, nor is there a transport mechanism to move the molecule to the cytosol. This ensures that all acetyl-CoA generated by PDH or fat oxidation will be used for energy production. However, as cellular energy demand falls, carbon atoms can be diverted into storage molecules such as glycogen and fatty acids. To move acetyl-CoA out of the mitochondria to the cytosol, it must first be converted to citrate, which can be transported by the TCA transport system.

When Cells Acquire Sufficient Energy Such That the Rate of Flux