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

1. Trioses with 3 C or 3 carbon atoms.
2. Tetroses with 4 C or 4 carbon atoms.
3. Pentose with 5 C or 5 carbon atoms.
4. Hexose with 6 C or six carbon atoms.
5. 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