Carbohydrates: Monosaccharides and Classification

Carbohydrates

Monosaccharides

Monosaccharides are the simplest form of carbohydrates and serve as the building blocks for more complex sugars. They are classified based on the number of carbon atoms and the type of carbonyl group present.

• Definition: Monosaccharides are single sugar molecules that cannot be hydrolyzed into simpler carbohydrates.

• General Formula: $C_nH_{2n}O_n$

• Examples: Glucose, Fructose, Ribose

Classification by Carbon Number

• Triose: 3 carbon atoms (e.g., Glyceraldehyde)

• Tetrose: 4 carbon atoms (e.g., Erythrose)

• Pentose: 5 carbon atoms (e.g., Ribose, Xylose)

• Hexose: 6 carbon atoms (e.g., Glucose, Fructose, Galactose, Mannose)

Classification by Functional Group

• Aldose: Contains an aldehyde group (e.g., Glucose, Ribose)

• Ketose: Contains a ketone group (e.g., Fructose, Ribulose)

Examples of Common Monosaccharides

Number of Carbons	Aldose Example	Ketose Example
3 (Triose)	Glyceraldehyde	Dihydroxyacetone
4 (Tetrose)	Erythrose	Erythrulose
5 (Pentose)	Ribose, Xylose	Ribulose, Xylulose
6 (Hexose)	Glucose, Mannose, Galactose	Fructose

Key Points

• Monosaccharides are classified by both the number of carbon atoms and the type of carbonyl group (aldehyde or ketone).

• Hexoses (6-carbon sugars) are the most common monosaccharides in nature.

• Pentoses are important components of nucleic acids (e.g., ribose in RNA).

Example: Glucose

• Glucose is a hexose (6 carbons) and an aldose (contains an aldehyde group).

• It is the primary energy source for most living organisms.

Example: Fructose

• Fructose is a hexose (6 carbons) and a ketose (contains a ketone group).

• It is found in fruits and honey and is the sweetest naturally occurring sugar.

Additional info: Classification of monosaccharides is fundamental for understanding carbohydrate metabolism and their roles in biological systems.