Monosaccharides can be found in the linear or ring form.
When in water they take the ring form.
This is lowest energy configuration, due to water's hydrogen bonding.
Since biological systems are in water this is the form in which monosaccharides almost always exist!
Four or more carbons are necessary for the formation of a ringed structure.
In glucose, carbon 1 combines with carbon 5. Notice how the hydrogen from the —OH group moves to the carbonyl group, converting it to a hydroxyl group.
When illustrating a ring structure, the carbons are often left out in order to draw the structure quickly or keep it from getting cluttered (as can be seen in the abbreviated ring structure below).
The quality of sweetness varies greatly among carbohydrates. In this regard, not all carbohydrates are created equal.
Sweetener
Relative Sweetness
Aspartame (an artificial sweetener, brand name Nutrasweet—not a carbohydrate)
200
Fructose (monosaccharide, “fruit sugar”)
1.3
Sucrose (disaccharide, “table sugar”)
1.0
Glucose (monosaccharide, “blood sugar”)
0.56
Galactose (monosaccharide)
0.50
Lactose (disaccharide, “milk sugar”)
0.25
Glycemic Index
How quickly carbohydrates raise your blood sugar (glucose) is rated by a scale called the glycemic index. There may be important health considerations with regards to this phenomenon. If you are interested in learning more, visit one of these websites: