Glucose, fructose and ribose are all sugars. When you consume foods that contain these compounds, you can burn them for energy or use them to make other molecules that serve functional and structural purposes. While glucose and fructose taste quite sweet and are used as sweeteners in foods, ribose serves important purposes but doesn't taste strongly sweet.
Glucose
Glucose is the most ubiquitous of the monosaccharides, which are single sugar unit molecules. You'll find glucose in table sugar, a disaccharide made up of glucose and fructose. Starch is also made up of glucose; it's a polysaccharide, meaning it's made of many sugar units, all of which are molecules of glucose. Glucose tastes slightly less sweet than table sugar, and it's the favorite fuel of your brain cells, explains Dr. Lauralee Sherwood in her book "Human Physiology."
Fructose
Like glucose, fructose tastes sweet; it's actually sweeter than table sugar. While there are structural differences between fructose and glucose -- it's these that are responsible for the significantly sweeter taste of fructose -- they share the chemical formula C6H12O6. Many sources of fructose are also sources of sucrose. Fruits, for instance, contain both sugars. A major difference between the two is that your cells need the hormone insulin to help them take up glucose from the blood, but this is not true of fructose.
Ribose
Ribose has a different chemical formula than glucose and fructose, but like the other two sugars, it's made up entirely of carbon, hydrogen and oxygen on a 1:2:1 ratio. It is much less sweet than the other sugars, so it's not commonly used as a sweetener for food. However, it still provides energy to your cells. The most common source of ribose in nature and in your body is RNA, ribonucleic acid, which is a type of genetic material.
Energy and Use
Glucose, fructose and ribose all contain four calories of energy per gram consumed. While they all serve important biological purposes, you can make them from one another, so you don't have individual requirements for glucose, fructose and ribose. You can also make deoxyribose, a sugar closely related to ribose, from the latter, explain Drs. Mary Campbell and Shawn Farrell in their book "Biochemistry." You use deoxyribose to form part of the backbone of DNA -- deoxyribonucleic acid -- which is your genetic material.
References
- “Biochemistry”; Reginald Garrett, Ph.D., and Charles Grisham, Ph.D.; 2007
- “Biochemistry”; Mary Campbell, Ph.D., and Shawn Farrell, Ph.D.; 2005
