Number of oxidation reactions in one turn of Tricarboxylic acid cycle is 

There are four oxidation reactions or dehydrogenation reactions in one turn of Citric acid cycle or Tricarboxylic acid cycle. The first one is formation of conversion of Citric acid to α-keto glutaric acid, second one conversion of α-keto glutaric acid to Succinic acid, third one is conversion of Succinic acid to Fumaric acid and the fourth one is formation of oxaloacetic acid from Malic acid.