This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Enzymes, Subject name: Biochemistry
In RBC the enzyme deficient is 
Select and explain. 
A. Hexokinase, B. Phosphofructokinase, C. Pyruvate kinase, D. Glycerol kinase
C: Pyruvate kinase
Answer: C: Pyruvate kinase 
Explanation: Pyruvate kinase is an enzyme that helps Cells turn sugar(glucose) into energy (Called Adenosine Triphsphate,ATP) in a process called glycolysis . Red cells rely on this process for energy and so, pyruvate kinase deficiency leads to a deficiency in energy and to premature red cell destruction .