You are investigating the metabolism of the amino acid aspartate in E. coli. After a transamination it enters the TCA cycle as oxaloacetate. If you radiolabel all the carbon atoms of aspartate equally, what fraction of the radioactivity will appear as CO2 during the first 2 turns of the TCA cycle? Draw the structure of OAA and indicate its labeling pattern after the second turn of the TCA cycle.