Oxaloacetate (OAA) from (C4) to
Combined with Acetyl coA (C2) was born as an acid.
Click the SIM (C6), and then click the frequently changing SIM acid.
Through Decarboxylation is C5.
(Alpha-ketoglutarate) before it was born.
Decarboxylation again as C4.
A whirl back to Oxaloacetate.