Final answer:
In the mitochondria, the transformation of pyruvate into acetyl CoA is a key step in ethanol metabolism, catalyzed by pyruvate dehydrogenase in the mitochondrial matrix.
Step-by-step explanation:
The step in ethanol (ETOH) metabolism that happens in the mitochondria is the transformation of pyruvate into acetyl CoA. This is carried out by the enzyme pyruvate dehydrogenase, which performs this oxidative decarboxylation reaction in the mitochondrial matrix. Pyruvate, a three-carbon molecule produced during glycolysis in the cytosol, is transported into the mitochondria, where it undergoes this crucial metabolic transformation. Additionally, the pyruvate dehydrogenase complex catalyzes the reduction of NAD+ to NADH, which will then enter the electron transport chain (ETC) to ultimately produce ATP.