Carbohydrate monomers are known as monosaccharide. This group includes glucose, C6H12O6, which is a key substance in biochemistry. Sugars that an animal eats are converted into glucose, which is then converted into energy to fuel the animal’s activities by respiration (see Cell Processes).
Glucose has a cousin called fructose with the same chemical formula. But these two compounds have different structures:
Glucose and fructose differ in one important way: glucose has double-bonded oxygen on the top carbon, while fructose has its double-bonded carbon on the second carbon. This difference is most apparent when the two monosaccharide are in their ring forms. Glucose generally forms a hexagonal ring (six sided), while fructose forms a pentagonal ring (five sided). Whereas fructose is the sugar most often found in fruits, glucose is most often used as the major source of energy for cellular activities.
