Model A flowchart. 1, Pyruvic acid. 2, O 2. 3, C O 2. 4, Acetyl-C o A. Model B flowchart. 1, Pyruvic acid. 2, C O 2. 3, O 2. 4, Acetyl-C o A. Which model represents the intermediate step between glycolysis and the citric acid cycle? Model