This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cell Physiology and Intercellular Connections, Subject name: Physiology
All of the following enzymes are active within a cell except: 
Select and explain. 
A. Trypsin, B. Fumerase, C. Hexokinase, D. Alcohol dehydrogenase
A: Trypsin
Answer: A: Trypsin 
Explanation: Ans. is 'a' ie Trypsin (Ref: Guyton and Hall, 10/e, p746; Harper's Biochem, 26/e, p76).Trypsin is a powerful pancreatic proteolytic enzyme which would digest the pancreatic cell that produced it, if not have been produce as a proenzyme (- its inactive form known as trypsinogen.) Trypsinogen is activated in the intestinal tract by enzyme called enterokinase.Pancreas has additional protective mechanism against self digestion by Trypsin - Secretion of trypsin inhibiter.All other options are enzymes of the glycolytic pathway which are in their active form within the cells.