Mechanism by which pyruvate from cytosol is trans- ported to mitochondria is

Ans. b (Proton symport) (Ref Harper 28th/153)Harper 28thA53:# Pyruvate, formed in the cytosol, is transported into the mitochondrion by a proton symporter.The Oxidation of Pyruvate to Acetyl-CoA Is the Irreversible Route from Glycolysis to the Citric Acid Cycle. Pyruvate, formed in the cytosol, is transported into the mitochondrion by a proton symporter.# Inside the mitochondrion, it is oxidatively decarboxylated to acetyl-CoA by a multienzyme complex that is associated with the inner mitochondrial membrane.# This pyruvate dehydrogenase complex is analogous to the a-KG dehydrogenase complex of the citric acid cycle.# Pyruvate is decarboxylated by the pyruvate dehydrogenase component of the enzyme complex to a hydroxyethyl derivative of the thiazole ring of enzyme-bound thiamin diphosphate, which in turn reacts with oxidized lipoamide, the prosthetic group of dihydrolipoyl transacetylase, to form acetyl lipoamide.# Thiamin is vitamin B, and in deficiency, glucose metabolism is impaired, and there is significant (and potentially life- threatening) lactic and pyruvic acidosis.# Acetyl lipoamide reacts with coenzyme A to form acetyl-CoA and reduced lipoamide.# The reaction is completed when the reduced lipoamide is reoxidized by a flavoprotein, dihydrolipoyl dehydrogenase, containing FAD.# Finally, the reduced flavoprotein is oxidized by NAD+that in turn transfers reducing equivalents to respiratory chain.