This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
Fluoride is used in 
Select and explain. 
A. Blood glucose estimation samples, B. Urine glucose estimation samples, C. Both 1 & 2, D. None of the above
A: Blood glucose estimation samples
Answer: A: Blood glucose estimation samples 
Explanation: The high energy compound phosphoenol pyruvate is generated from 2-phosphoglycerate by the enzyme enolase. This enzyme requires Mg2+ or Mn2+ and is inhibited by fluoride. For blood  glucose estimation in the laboratory, fluoride is added to the blood to prevent glycolysis by the cells, so that blood glucose is correctly estimated.