Question

Trace the isotopic label of --[¹⁴C]-glycine through one round of the citric acid cycle. How many ATPs equivalents would be made if the ETS was working?

The labeled carbon is the alpha carbon. Please show all the structures showing the labeled carbon all the way through.

Answer 1

In the cycle, the alpha marked carbon is the labeled carbon of glycine.

The ATP generating steps in this cycle are :

• Pyruvate to acetyl Co-A = 1 NADH = 2.5 ATP
• Isocitrate to alpha-keto glutarate = 1 NADH = 2.5 ATP
• Alpha-keto glutarate to succinyl CoA = 1 NADH = 2.5 ATP
• Succinyl CoA to succinate = 1 GTP = 1 ATP
• Succinate to fumarate = 1 FADH2 = 1.5 ATP
• Malate to oxaloacetate = 1 NADH = 2.5 ATP

Hence, total ATP produced = 2.5+2.5+2.5+1+1.5+2.5 = 12.5