Julia Howell, age 15, of Las Vegas, Nev., for her question:
WHAT IS GLUCOSE?
A white crystalline sugar, about half as sweet as sucrose or table sugar, is called glucose. It is produced during photosynthesis, or the food making process, in green plants.
Glucose is in the class of food called carbohydrate. It can be found in many sweet fruits and it makes up about one third of honey.
All living cells, including those of the human body, can use glucose as a direct source of energy.
Glucose is a sugar called a monosaccharide, or sugar with a simple structure. And because of this simple structure, glucose does not need to be digested in the human body as most foods do. It is absorbed through the small intestine directly into the blood.
More complex carbohydrates, such as sucrose or starch, must be digested to monosaccharides before they can be absorbed.
Sometimes extra glucose in the body is stored in the liver and muscles as glycogen. Some glucose may also be changed to fat. Then when extra energy is needed, stored glycogen can be changed back to glucose.
Under normal conditions, which is most of the time, the blood contains about 0.1 percent glucose.
In a person with diabetes, the amount of glucose in the blood increases because body cells cannot absorb the sugar. The amount builds up in the blood, and the excess passes into the urine and out of the body.
People who are not able to take food in a normal way are often fed with glucose solutions intravenously, or by injections directly into the blood.
Glucose can be made commercially from starch, which is mixed with acid and heated under steam pressure. If this conversion is complete, the glucose is a pure powder and sold under the name of dextrose.
If the conversion of starch to glucose is not complete, the mixture will contain glucose and other sugars called glucose syrup. This form is called corn syrup.
Corn syrup is used widely in foods and beverages, especially in candy, baking goods, brewing, fruit canning and soft drinks.
Carbohydrates provide living things with much of the energy they need to operate muscles and nerves and to build and repair plant and body tissues.
Carbohydrates contain carbon, hydrogen and oxygen. These elements are combined in the following formula for glucose: six parts carbon, 12 parts hydrogen and six parts oxygen.
Sucrose, or table sugar, has this chemical formula: 12 parts carbon, 22 parts hydrogen and 11 parts oxygen.