Question

how many pyruvate molecules must enter the mitochondrion,  fueling the Citric acid cycle and electron transport chain in order to produce 50 ATP?

Answer 1

A minimum of four pyruvate molecules must enter the mitochondria to generate 50 ATP at the end of citric acid cycle and electron transport chain(ETC).

Two pyruvate produces 2 ATP and 8 NADH+H+ reactions, in TCA cycle (citric acid cycle), 24 ATPs are produced directly, and through 8 NADH+H+ reactions, via two FADH2 4 ATPs are produced in the ETC. Therefore one pyruvate molecule on entering the mitochondria generates 15ATP, hence four pyruvate molecules are required to enter the mitochondria for the production of 50 ATP. In actual, 60 ATPS are produced through 4 pyruvates and only 45 ATP with 3 pyruvate molecules. hence 4 pyruvate molecules are required.