This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Structure and function of protein, Subject name: Biochemistry
Number of optical isomers possible for Glucose is 
Select and explain. 
A. 2, B. 4, C. 8, D. 16
D: 16
Answer: D: 16 
Explanation: Leber van Hoft rule for the number of stereoisomers is 2n where 'n' is the number of chiral centers. In open chain of glucose, there are 4 chiral centers. Hence it is 24 =16 isomers.Glucose, with four asymmetric carbon atoms, can form 16 isomers.Sugars have large numbers of stereoisomers because they contain several asymmetric carbon atoms.Ref: Harper&;s Biochemistry; 30th edition; Chapter 15; Carbohydrates of Physiological Significance