Tim Miller, age 15, of Poughkeepsie, N.Y., for his question:
WHAT IS GLUCOSE?
Glucose is a white crystalline sugar, about half as sweet as sucrose or table sugar. It is in the class of food called carbohydrate and is produced during the photosynthesis or food making process in green plants.
Glucose is found in many sweet fruits and 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. Because of its simple structure, glucose doesn't need to be digested or broken down into simple units in the human body as most foods do.
Glucose 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.
After a meal rich in carbohydrates, some of the extra glucose is stored in the liver and muscles as glycogen. Some glucose may also be changed to fat. When quick energy is needed, stored glycogen can be changed back to glucose again.
The blood normally contains about 0.1 percent of glucose. In the disease diabetes, the amount of glucose in the blood increases because the cells cannot absorb glucose. The amount of glucose builds up in the blood and the excess passes into the urine and out of the body.
Patients who are unable to take food in a normal way are often fed with glucose solu
tions intravenously, or injected directly into the blood.
Glucose is made commercially from starch. Such starch is mixed with acid and heated under steam pressure. If this conversion or change is completed, the glucose is a pure powder and sold under the name dextrose.
If the conversion of starch mixed with acid is not completed and the mixture contains glucose with other sugars, it is called glucose syrup. It is also sometimes called starch syrup on corn syrup.
Both dextrose and glucose syrup are used widely in foods and beverages, especially in candy, baked goods, fruit canning, brewing and soft drinks.
Carbohydrates contain the chemical elements carbon, hydrogen and oxygen. These elements are in carbohydrates in about the proportions of one atom each of carbon and oxygen and two atoms of hydrogen.
Carbohydrates form a large group of compounds and include all sugars and starches. The sugar used to sweeten food and drink is a carbohydrate. So is cellulose, the substance that makes up a large part of the cell walls of plants, and gylcogen, a kind of starch that is found in animals.