Sucrose and glucose are both chemically classified as saccharides, or sugars. They're both carbohydrate compounds, chemically related to starch, but with a sweet taste, because they bind to sweetness receptors on the tongue. With regard to how they're processed by the body, there are many similarities between sucrose and glucose.
Features
While sucrose and glucose are both sugars, there are some differences between them. Glucose is a monosaccharide, meaning it's composed of a single sugar unit, according to Garrett and Grisham's "Biochemistry." Sucrose, on the other hand, is a disaccharide, meaning it's composed of two sugar units. In fact, one of the sugar units in sucrose is glucose, while the other is a sugar unit called fructose, or fruit sugar.
Function
Both sucrose and glucose have similar functions in the body -- they provide cells with energy. Sucrose, like all disaccharides, must be chemically split into its constituent monosaccharides before the cells that line the intestine can absorb the sugar unit. Glucose, however, can be absorbed without any chemical modification. Once in the bloodstream, notes Campbell and Farrell's "Biochemistry," both ingested glucose and the constituents of sucrose -- glucose and fructose -- become available to the liver and body cells.
Considerations
There are some minor differences in ways glucose and fructose, which comes from sucrose, are taken up by body cells. Glucose uptake is regulated by the hormone insulin, which is produced by the pancreas, explains "Human Physiology." For this reason, diabetics who don't produce or can't respond to insulin can end up with very high blood glucose levels after a meal. Fructose uptake isn't regulated by insulin.
Metabolism
Once inside the cells, glucose and the sucrose derivative fructose are processed differently. Glucose immediately enters the process of glycolysis, and from there -- provided that cells have sufficient oxygen supply to burn sugar -- enters the Kreb's cycle of metabolism. This results in the extraction of a large quantity of energy from glucose. Fructose has to enter glycolysis through slightly different means, says Garrett and Grisham's "Biochemistry," but the net energy yield is the same as that of glucose.
Expert Insight
As components of diet, glucose and sucrose are relatively equivalent. Both provide cellular energy, and both contain approximately 4 calories of energy per gram of sugar, notes "Human Physiology." Both cause hyperglycemia in diabetics, since sucrose contains glucose. Because fructose is a very sweet sugar compared with glucose -- almost twice as sweet -- sucrose tastes sweeter on the tongue than glucose. As a result, it may be possible to obtain a similar sweetness in foods with less sucrose than glucose. Of the two sugars, sucrose is the more common in the grocery store and in the kitchen -- it's colloquially called "table sugar" and is what is sold in bags and packets as cooking sugar.
References
- "Biochemistry"; Reginald Garrett, Ph.D. and Charles Grisham, Ph.D.; 2007
- "Biochemistry"; Mary Campbell, Ph.D. and Shawn Farrell, Ph.D.; 2005
- "Human Physiology"; Lauralee Sherwood, Ph.D.; 2004
