Glucose & Stereochemistry

Glucose is a simple sugar.

Stereochemistry is the study of stereoisomers, compounds with identical molecular formulas but different 3-D arrangements of their atoms. Stereoisomers are a subclass of isomers, a broader term referring to any two compounds with identical molecular formulas but different structural formulas. The simple sugar molecule glucose is one common example.

Types

Aldohexose sugars have six carbons and an aldehyde group, which is an OH group attached to a terminal carbon, at one end of the chain. There are 16 possible stereoisomers of an aldohexose sugar, two of which are called glucose.

Function

One of the glucose stereoisomers is an enantiomer of the other. An enantiomer has a mirror-image structure that cannot be superimposed on the other enantiomer, rather in the same way your right hand is a mirror image of your left but the two cannot be superimposed--a right hand won't fit into a left-hand glove. The two glucose enantiomers are called L-glucose and D-glucose.

Considerations

Only D-glucose is biologically active; your cells cannot use L-glucose in the same way they would D-glucose. D-glucose is sometimes called dextrose, especially in the food industry. D-glucose can adopt either a six-membered ring configuration or a chain shape. In solution, most glucose exists in the six-membered ring configuration.

References

• "Biology, 8th Edition"; Neil Campbell, Jane Reece, Lisa Urry, Michael Cain, Steven Wasserman, Peter Minorsky, Robert Jackson; 2008.
• 3D Chem: Glucose, Molecule of the Month
• California State University, Dominguez Hills: Chemistry 240, Structure of Glucose