The main sugar that the body makes from the three elements of food-- proteins, fats, and carbohydrates-- but mostly from carbohydrates. Glucose is the major source of energy for living cells and is carried to each cell through the bloodstream. However, the cells cannot use glucose without the help of insulin.
From the BioTech Dictionary at http://biotech.icmb.utexas.edu/; originally from PharmInfoNet. For further information see the BioTech homenode.