Classification of Carbohydrates

Last Updated : 20 Feb, 2024

Carbohydrates are organic compounds composed of carbon, hydrogen, and oxygen atoms. They are classified based on their structure and complexity such as Simple and Complex Carbohydrates. Carbohydrates play crucial roles in various biological processes, including energy storage, structural support, cell-cell recognition, and cell signaling.

In this article, we will discuss all the various classifications of carbohydrates such as Monosaccharides, Disaccharides, Oligosaccharides, and Polysaccharides.

Classification-of-Carbohydrates

Table of Content

What are Carbohydrates?
Types of Carbohydrates
Simple Carbohydrates
Complex Carbohydrates
Uses of Carbohydrates

What are Carbohydrates?

Carbohydrates are organic compounds made up of carbon, hydrogen, and oxygen atoms, usually with a hydrogen-oxygen atom ratio of 2:1. They are one of the major macronutrients, along with proteins and fats, and serve as a primary source of energy for living organisms.

Carbohydrates are found in a wide variety of foods, including fruits, vegetables, grains, legumes, dairy products, and sweets. They come in various forms, ranging from simple sugars like glucose and fructose to complex carbohydrates like starches and fibers.

The atoms of carbon, hydrogen, and oxygen make up the organic molecule known as carbohydrates.
Combined with proteins and fats, they make up the trio of macronutrients that are critical to human health.
Fuel for cellular operations and other physiological functions, carbohydrates are the body’s main source of energy.

Formula for Carbohydrates

General Formula for Carbohydrates is C_nH₂_nO_n.

Where n represents the number of carbon atoms in the molecule.

However, this formula applies mainly to monosaccharides, the simplest form of carbohydrates. For example, the chemical formula for glucose, a common monosaccharide, is C₆H₁₂O₆.

Note: Monosaccharides have a basic structural formula of (CH₂O)_n, reflecting the fact that they can be thought of as hydrates of carbon.

Types of Carbohydrates

Carbohydates can be classified based on the complexity of the strucutre as

Simple Carbohydates
- Monosaccharides
  - Glucose
  - Fructose
  - Galactose
- Disaccharides
  - Sucrose
  - Lactose
  - Maltose
Complex Carbohydrates
- Oligosaccharides
  - Raffinose
  - Stachyose
- Polysaccharides
  - Starch
  - Glycogen
  - Cellulose

Let’s discuss these types and their examples in detail as follows.

Simple Carbohydrates

Simple carbohydrates, also known as simple sugars, are composed of one or two sugar molecules or saccharides. They are typically quickly digested and absorbed by the body, leading to a rapid increase in blood sugar levels.

Simple Carbohydrates can be further classified as:

Monosaccharides
Disaccharides

Monosaccharides

Single sugar molecules make up monosaccharides, the most basic kind of carbohydrates. They are the fundamental components of more complex carbs and the body’s main energy source. Some of the common examples are:

Glucose: Often referred to as blood sugar, it is the primary source of energy for cells in the body.
Fructose: Found naturally in fruits, honey, and some vegetables, it is the sweetest naturally occurring sugar.
Galactose: Found in dairy products and certain fruits and vegetables, it is less common than glucose and fructose.

Disaccharides

Glycosidic bonds are created when two monosaccharide molecules undergo a condensation process, forming disaccharides. They offer a rapid energy source and are frequently present in meals and drinks. Common examples of disaccharides are:

Sucrose (glucose + fructose): Common table sugar composed of one molecule of glucose bonded to one molecule of fructose. It is found in sugarcane, sugar beets, and various sweetened foods.
Lactose (glucose + galactose): Also known as milk sugar, it is composed of one molecule of glucose bonded to one molecule of galactose. It is found in milk and dairy products.
Maltose (glucose + glucose): Formed during the breakdown of starch, maltose consists of two glucose molecules bonded together. It is found in germinating grains and malted foods.

Complex Carbohydrates

Complex carbohydrates, also known as polysaccharides, are composed of long chains of sugar molecules, which may include hundreds or even thousands of individual sugar units linked together.

They are typically found in whole, unprocessed foods and provide a slower and more sustained release of energy compared to simple carbohydrates. Complex carbohydrates can further be classified as:

Oligosaccharides
Polysaccharides

Oligosaccharides

These sugar molecules are short chains that typically comprise three to ten distinct monosaccharide units. Beans, onions, and several fruits are among the foods that contain them. As prebiotics, oligosaccharides can encourage the growth of good bacteria in the digestive system. Some of the most common examples of oligosaccharides are:

Raffinose: Raffinose is composed of three monosaccharide units i.e., galactose, glucose, and fructose and commonly found in foods such as beans, cabbage, broccoli, Brussels sprouts, and whole grains.
Stachyose: Stachyose, another oligosaccharide, consists of four monosaccharide units, including two galactose molecules, one glucose molecule, and one fructose molecule. Like raffinose, stachyose is abundantly present in foods such as beans, legumes, and certain vegetables.

Polysaccharides

Polysaccharides are lengthy chains of sugar molecules made up of more than ten monosaccharide units. They are huge, complex carbohydrates and have a variety of uses in living things. Some of common examples include:

Starch: Starch is a polysaccharide composed of long chains of glucose molecules bonded together. It is commonly found in foods such as grains (wheat, rice, oats), tubers (potatoes, yams), and legumes (beans, lentils).
Cellulose: Cellulose is a polysaccharide consisting of long chains of glucose molecules linked together in a linear fashion. It is a major structural component of plant cell walls, providing rigidity and strength to plant cells.
Glycogen: Glycogen is a polysaccharide that serves as a short-term energy storage molecule in animals, particularly in the liver and muscles. Similar in structure to starch but more highly branched, glycogen consists of long chains of glucose molecules with numerous branching points.

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Monosaccharide

Polysaccharides

Disaccharides

Uses of Carbohydrates

Some of the most common uses of carbohydrates are:

Energy Source: The body uses carbohydrates as its main energy source. An easy sugar to digest, glucose provides cells with the energy currency they need to function: adenosine triphosphate, or ATP.
Storage of Energy: Starch is the form in plants, and glycogen is the type in mammals. In times of high energy demand or restricted glucose intake, these storage forms enable organisms to store surplus glucose for later use.
Structural Support: Cell walls and exoskeletons, respectively, receive stiffness and structural support from certain carbohydrates, such as chitin in fungi and arthropods and cellulose in plants.
Carbohydrates: Carbohydrates are involved in the identification and communication between cells in the body. They are a component of glycolipids and glycoproteins, which are crucial for immunological response, cell adhesion, and cell signaling.
Dietary Fiber: Although some carbohydrates, such as dietary fiber, are indigestible to humans, they are essential for preserving intestinal health. Fiber helps encourage regular bowel movements, gives stool more volume, and may guard against constipation and other digestive issues.

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Galactose

Glucose Chemical Formula

Maltose Formula

Lactose Formula

Sucrose(C₁₂H₂₂O₁₁)