This molecule is D-glucose, C6H12O6: It is the glucose from food and drink that builds up inside a diabetic when there is no insulin available to allow the glucose to diffuse into the cells. When this happens, the diabetic will have a high blood-sugar level, which can be measured using a glucose monitor.

The more common form of glucose has a ring structure. This is alpha-D-glucose:


This is beta-D-glucose:



Sucrose is a disaccharide derived from glucose and fructose (it is essentially glucose and fructose connected by an acetal linkage). It is one of the only natural chemicals that are consumed by humans in unmodified form (like water and NaCl). It is broken down by enzymes in the body to give glucose, which is then diffused into the cells to give the body energy.