Citric Acid Cycle -matching carbons

[jenzao]

Citric Acid Cycle --matching carbons

Which glucose carbons are pyruvate carbons from? I've been trying to get this for hours. please help.. Also how do you trace carbons along the ciric acid cycle?

 

[Renge Ishyo]

Each pyruvate is a 3 carbon molecule and glucose is a 6 carbon molecule. Therefore, half of the carbons in a glucose molecule go to each of the two pyruvate molecules. The step where the molecule is cut in half I believe is the step where fructose-1,6-bisphosphate is cleaved by aldolase so you should be able to see which carbons go where by analyzing the result of that step. If you want to track the carbons, the easiest thing to do is to just number them on each step of the pathway.