Carbohydrates: Structure, Classification, and Biological Roles

Classes of Carbohydrates

Overview of Carbohydrates

Carbohydrates are a major class of biomolecules, commonly known as sugars, that serve as a primary source of energy and have important structural and functional roles in living organisms.

• Energy Source: Carbohydrates are metabolized to provide energy for cellular processes.

• Structural Roles: Simple sugars are components of genetic material such as DNA and RNA.

• Cellular Markers: Certain carbohydrates act as markers on cell surfaces, aiding in cell recognition and immune response.

• Health Implications: Some carbohydrates are involved in diseases such as diabetes and lactose intolerance.

Classification of Carbohydrates

Carbohydrates are classified based on the number of simple sugar units they contain:

• Monosaccharides: The simplest carbohydrates, consisting of a single sugar unit. They cannot be hydrolyzed into smaller carbohydrates. Example: Glucose ($C_6H_{12}O_6$).

• Disaccharides: Composed of two monosaccharide units joined together. Example: Sucrose ($C_{12}H_{22}O_{11}$), which can be hydrolyzed into glucose and fructose.

• Oligosaccharides: Contain three to nine monosaccharide units. ABO blood group markers are examples of oligosaccharides.

• Polysaccharides: Large molecules formed by joining ten or more monosaccharide units. They can be linear or branched. Example: Starch in plants, which is a branched polymer of glucose.

Visual Representation of Carbohydrate Classes

Class	Number of Monosaccharide Units
Monosaccharide	1
Disaccharide	2
Oligosaccharide	3–9
Polysaccharide	10–10,000

Additional info:

• Monosaccharides have the general formula $C_n(H_2O)_n$, where $n \geq 3$.

• Complex carbohydrates include both digestible (starches) and indigestible (fiber) forms.