The list that follows gives the common sugars and their descriptors.
•Ribose = aldo-pentose •Glucose = aldo-hexose •Galactose = aldo-hexose •Mannose = aldo-hexose •Fructose = keto-hexose Diastereomers Figure 2.149 - Diastereomers Sugars may have multiple asymmetric carbons and thus differ from each other in the configuration of hydroxyl groups on asymmetric carbons.
Figure 2.150 - Epimers - D-Galactose and D-Glucose differ only in the configuration of carbon #4 Enantiomers and epimers Figure 2.151 - Enantiomers - D-Glucose (left) and L-Glucose (right) are mirror If two sugars are identical except for having one hydroxyl configured differently (such as images glucose and galactose - Figure 2.150), they are diastereomers known as epimers.
If the configuration of all of the hydroxyls of one sugar is exactly the opposite of their configuration in another sugar, the two sugars are mirror images of each other (Figure 2.151). Please note that due to the way sugars are named, L-glucose is the mirror image of Dglucose.
Certain carbohydrates are an important storage and transport form of energy in most organisms, including plants and animals.
There are four types of carbohydrates, named by the number of sugar molecules they contain.
On the basis of their degree of polymerization, they can be classified as: Arienti G.
2000 Mariani Costantini A., Cannella C., Tomassi G.
“Modern nutrition in health and disease” 9th ed., by Lippincott, Williams & Wilkins, 1999 Stipanuk M.
Biochemical, physiological, and molecular aspects of human nutrition.