Glucose, sucrose and lactose
Biochemically, glucose, sucrose and lactose are sugars. Unlike glucose and sucrose, lactose has a very sweet taste but the three molecules affect the body similarly and three can be used to anticipate the needs of cellular energy. Glucose is a common sugar found in table sugar and starch. Sucrose is table sugar and lactose is milk sugar.
Glucose, sucrose and lactose fall in biochemical class of carbohydrates. The carbohydrates are composed of the elements carbon, hydrogen and oxygen and are composed of one or more saccharides. Glucose is a monosaccharide and consists of a single sugar molecule, while lactose and sucrose are disaccharides both. Each contains a glucose unit, sucrose contains a fructose unit and lactose contains a galactose unit.
In the body, these three carbohydrates can be used to meet the needs of cellular energy. The intestine can only absorb monosaccharides, so that sucrose and lactose must be divided into units of constituent sugars before being absorbed. Sugars, once absorbed into the bloodstream, are absorbed by the cells and metabolized for energy through a pathway called glycolysis, which means “sugar division.”
Structurally, glucose is quite similar to the constituent molecules of sucrose and lactose. Fructose and galactose are both monosaccharides as glucose and the three share the same chemical formula – C6H12O6. There are structural differences between the molecules and are important enough to require different enzymes are involved in the metabolism of sugar units. Furthermore, enzymes are required to split apart the sugar units in lactose and sucrose before absorption of the components of monosaccharide molecules. Although glucose, sucrose and lactose are chemically classified as sugars, not all sugars bind to receptors on the tongue of sweetness in the same manner so that there are sweeter than other sugars. Sucrose is the one with the sweetest of the three sugar flavor and is approximately sweeter than glucose third. Lactose is the least sweet of the three and is only about 15 percent as sweet as table sugar.
An important difference between lactose and other sugars is that all humans have the ability to split sucrose into the digestive tract and absorb components but many individuals lack the enzyme lactase which decomposes lactose into glucose and galactose. The result is that these people are lactose intolerant. The undigested lactose moves in the lower intestine and can cause cramps and gases.