Sucrose and glucose both fall into the broad category of carbohydrates, which is a class of macronutrient compounds. They're both sugars, and they both taste sweet, but there are some structural and chemical differences between the two, in terms of how they are processed by your body after you consume them.
Glucose Chemistry
Glucose is one of the simplest and most ubiquitous carbohydrates in nature. A carbohydrate is a chemical compound made up of carbon, hydrogen and oxygen, explain Dr. Reginald Garrett and Dr. Charles Grisham in their book "Biochemistry." Glucose, specifically, is a monosaccharide, which means it consists of a single sugar ring. The chemical formula for glucose is C6H12O6. Because it's a sugar, glucose tastes sweet. It binds to sweetness receptors in the human mouth.
Sucrose Chemistry
Like glucose, sucrose is a sugar. It is not, however, a monosaccharide. Dr. Mary Campbell and Dr. Shawn Farrell, in their book "Biochemistry," explain that sucrose is a disaccharide, meaning that it is made up of two monosaccharide rings. One is glucose, and the other is fructose, a related monosaccharide. The chemical formula for sucrose is C12H22O11. Like glucose, sucrose binds to sweetness receptors in the human mouth, and has a sweet taste.
Reducing Sugars
Some carbohydrates are classified as "reducing sugars" in biochemistry, while others are not. Reducing sugars can participate in chemical reactions that non-reducing sugars aren't able to. For instance, reducing sugars can change the chemical orientation of certain of their bonds, while non-reducing sugars can't. Glucose is a reducing sugar, and sucrose is not. The ramifications of this include that glucose can form bonds to other monosaccharide molecules, but sucrose isn't able to.
Formation of Chains
Glucose is the chemical building block for many larger molecules. It is sometimes found in nature on its own, explain Garrett and Grisham, but it's more commonly found bound to one or more other monosaccharides to form disaccharides like sucrose or very long chains of glucose. Starch and fiber both consist of long chains of glucose molecules. Sucrose doesn't have the ability to form chains, and sucrose is not a constituent of any larger molecules in nature.
Relative Sweetness
Glucose tastes somewhat less sweet than sucrose. The reason for this is that sucrose contains fructose, which is a sweet-tasting sugar ring that binds more tightly than glucose does to the sweetness receptor in the human mouth. As a result, table sugar -- which is made up of sucrose -- tastes sweeter than syrups consisting of pure glucose, such as corn syrup. Regardless of the perception of sweetness, both glucose and sucrose contain 4 Calories per gram.
References
- "Biochemistry"; Reginald Garrett, Ph.D., and Charles Grisham, Ph.D.; 2007
- "Biochemistry"; Mary Campbell, Ph.D., and Shawn Farrell, Ph.D.; 2005
