The tricarboxylic acid cycle is initiated by the condensation of?

The TCA cycle stas with reaction between the acetyl moiety of acetyl-CoA and the four-carbon dicarboxylic acid oxaloacetate, forming a six-carbon tricarboxylic acid, citrate. In the subsequent reactions, two molecules of CO2 are released and oxaloacetate is regenerated. Only a small quantity of oxaloacetate is needed for the oxidation of a large quantity of acetyl-CoA; it can be considered as playing a catalytic role, since it is regenerated at the end of the cycle. Ref: Bender D.A., Mayes P.A. (2011). Chapter 17. The Citric Acid Cycle: The Catabolism of Acetyl-CoA. In D.A. Bender, K.M. Botham, P.A. Weil, P.J. Kennelly, R.K. Murray, V.W. Rodwell (Eds), Harper's Illustrated Biochemistry, 29e.