Question

How is acetyl CoA transported out of mitochondria?

Answer 1

Acetyl-CoA is a molecule involved in a wide range of metabolic activities in protein, carbohydrate, and lipid metabolism. Its primary job is to transport the acetyl group to the citric acid cycle, where it is oxidised to provide energy. Acetyl-CoA is produced in the mitochondrial matrix by oxidative decarboxylation of pyruvate from glycolysis, oxidation of long-chain fatty acids, or oxidative degradation of specific amino acids. The acetyl-CoA is then oxidised for energy production in the TCA cycle.
CoA (coenzyme A) and its derivatives play an important role in cardiac energy metabolism regulation. This includes serving as an allosteric regulator of cardiac energy metabolism as well as a critical role as a substrate and product in energy metabolic pathways.

Complete answer:
Acetyl CoA is not able to get through the mitochondrial membrane. The oxidative decarboxylation of pyruvate or the oxidation of fatty acids create it in the mitochondria. The acetyl CoA enters the TCA cycle when energy is required. If there is enough energy, acetyl CoA is used in the production of fatty acids. Because fatty acid production takes place in the cytoplasm, acetyl CoA must be transferred from the mitochondria to the cytosol. It is transported out of mitochondria as citrate because it cannot pass the membrane. Citrate is made when the enzyme citrate synthase combines acetyl CoA and oxaloacetate. Citrate is converted back to oxaloacetate and acetyl CoA is released once it reaches the cytoplasm.
Citrate is generated from oxaloacetate and acetyl-CoA and delivered to the cytosol via the tricarboxylate anion carrier system, where it is broken into acetyl-CoA and oxaloacetate. The gluconeogenic pathway may finally convert the oxaloacetate generated from pyruvate to glucose (through malate).

Note:
Fatty acids are unsaturated or saturated carboxylic acids (or organic acids) having long aliphatic tails (long chains).
Saturated fatty acids- The fatty acid is saturated if there are no carbon-carbon double bonds. Because of their tendency to pack their molecules together, saturated fatty acids have greater melting temperatures than unsaturated acids of the same size. This results in a straight rod-like structure.
Unsaturated fatty acids- When a fatty acid has more than one double bond, it is called an unsaturated fatty acid. The cis-double bond(s) in unsaturated fatty acids cause a structural kink that prevents them from grouping their molecules in a straight rod-like structure.