Monosaccharide Definition
Monosaccharides are known as simple sugars with a formula Cn (H2O)n. In Greek the word monosaccharide means (mono-one and saccharide- sugar). They are the simplest group of carbohydrates that can not be hydrolyzed more. The definition of monosaccharide is such sugars that on hydrolysis yield no further lower sugars. The following articles are about classifications and monosaccharide examples.
Monosaccharides classification
Based on the functional group they are classified into the following
Aldoses: here the functional group is aldehyde examples are glyceraldehyde and glucose.
Ketoses: here the functional group is keto examples are dihydroxyacetone and fructose.
Number of carbons |
Aldoses |
Ketoses |
| 3 | Aldotriose Glycerose CHO-CHOH-CH2OH | Ketotriose or triulose Dihydroxyacetone CH2OH-CO-CH2OH |
| 4 | Aldotetrose Erythrose CHO- (CHOH)2-CH2OH | Ketoterose or terulose Erythrulose CH2OH-CO-CHOH-CH2OH |
| 5 | Pentose or Aldopentose Ribose CHO-(CHOH)3-CH2OH | Pentulose or Ketopentose Ribulose CH2OH-CO-(CHOH)2-CH2OH |
| 6 | Hexose or aldohexose Glucose CHO-(CHOH)4-CH2OH | Hexulose or Ketohexose Fructose CH2OH-CO-(CHOH)3-CH2OH |
Based on the number of carbon atoms they are divided into
- Trioses with 3 C or 3 carbon atoms.
- Tetroses with 4 C or 4 carbon atoms.
- Pentose with 5 C or 5 carbon atoms.
- Hexose with 6 C or six carbon atoms.
- Heptose with 7 C or 7 carbon atoms.
Some monosaccharide examples and their source, and biochemical importance are as follows
Monosaccharides |
Source |
Biochemical functions |
| Trioses Glyceraldehyde (an aldose) Dihydroxyacetone (a ketose) | Found in the cell as a phosphate | Both are intermediate in the glycolysis cycle. |
| Tetroses Erythrose Threose | Widespread | Yield tartaric and mesotartaric acids |
| Pentoses D-ribose D-Deoxyribose D-Xylose |
RNA DNA Glycoproteins |
RNA structure DNA structure Function of glycoproteins |
| Hexose D-Glucose D-mannose D-galactose D-Fructose |
Starch, Glycogen, and Cellulose Plant polysaccharide Milk Fruits and Honey |
Energy source Converted into glucose Structure of polysaccharides Glycolysis cycle |
