Question

How many CO2 molecules in a single turn aroudn the reverse citric acid cycle all the way to pyruvate? A) 1 B) 2 C ) 3 D) 4

Answer 1

Reverse citric acid cycle is carbon fixation pathway observed in green sulfur bacteria and green nonsulfur bacteria. In reverse citic acid cycle, most of the citric acid cycles' enzymes are used but in reverse direction. Ferredoxin, the non-heme iron sulfur protein acts as an electron donor. In each cycle of reverse citric acid cycle 3 carbon dioxide (CO₂) molecules are used to produce pyruvate. One molecule of CO₂ during succinyl CoA to ketoglutarate, one molecule during ketoglutarate to isocitrate and one molecule during Acetyl CoA to pyruvate. Thus, option C is correct.