Sucrose
Definition and meaning of Sucrose in chemistry.
Sucrose is a disaccharide carbohydrate composed of one molecule of glucose and one molecule of fructose linked via an alpha-1,2-glycosidic bond. It is a naturally occurring non-reducing sugar produced primarily in plants to transport energy from the leaves to other tissues. The lack of a free anomeric carbon means sucrose cannot form reactive aldehyde or ketone groups in solution.
In more detail
Sucrose is synthesized by plants as a primary transport form of carbon and energy, moving from leaves to other organs via the phloem. The alpha-1,2-glycosidic bond connects the C1 anomeric carbon of alpha-D-glucose to the C2 anomeric carbon of beta-D-fructose. This structural arrangement locks both monosaccharide rings in their closed forms, preventing mutarotation and rendering sucrose a non-reducing sugar, meaning it does not react with Tollens' or Fehling's reagents. When consumed by mammals, the membrane-bound enzyme sucrase-isomaltase catalyzes the hydrolysis of sucrose in the brush border of the small intestine, yielding free glucose and fructose which are then rapidly absorbed into the bloodstream. In industrial applications, sucrose is crystallized from the juices of sugarcane or sugar beets through a multi-step process of extraction, purification, concentration, and crystallization, resulting in a highly pure chemical substance used globally.
Key facts
| Field | Biochemistry |
|---|---|
| Formula | C12H22O11 |
| Molar mass | 342.30 g/mol |
| State | Solid (crystalline) |
| Melting point | 186 °C (decomposes) |
Table sugar used for sweetening coffee and baking is nearly pure crystalline sucrose extracted from sugarcane or sugar beets.
Frequently asked questions
Why is sucrose a non-reducing sugar?
Sucrose is non-reducing because the glycosidic bond is formed directly between the anomeric carbons of both glucose and fructose. This structural linkage prevents the rings from opening to form reactive free aldehyde or ketone groups.
How is sucrose digested in the human body?
In the small intestine, the digestive enzyme sucrase breaks the glycosidic bond, separating sucrose into equimolar amounts of glucose and fructose, which are then absorbed into the blood.