Carbohydrates | Classification, Functions, & Food

Composition of Foods

Food can be classified into three categories according to their functions in the body. 
1. Energy-giving foods ➝ Carbohydrates and Fats
2. Bodybuilding foods ➝  Proteins
3. Protective foods       ➝   Vitamins and Minerals

Energy-giving foods

Foods rich in Carbohydrates and fats are called energy-giving foods. They provide energy to the human body to carry out activities. Dried fruits, rice, wheat, ghee etc are all the good source of energy.

Bodybuilding foods

Foods rich in proteins are called bodybuilding foods. These foods help for body growth and repair tissues. They also provide energy to the body. Milk, egg, meat, liver, soybeans etc are all goods sources of the bodybuilding foods.

Protective foods

Foods rich in vitamins and minerals are called protective and regulatory foods. They are essential for the maintenance of body temperature, muscle contraction, controlling of water balance, clotting of blood, removal of waste products from the body and maintaining the proper heartbeat. Green vegetables, fruits, milk etc are all the good sources of protective foods. 


A carbohydrate is a biomolecule which consists of three elements carbon(c), hydrogen(h), and Oxygen(o) atoms. It is also known as saccharides. The general formula of carbohydrate is Cx(H2O)y where (x may be different from y). It contributes about 45% of calories in most of the diets.
Glucose is the simplest carbohydrates which give an instant source of energy. One gram of glucose will give you almost 4.2 kilocalories energy.

Classification of  Carbohydrates

Carbohydrates are classified on the basis of sugar or saccharide molecules. They are divided into two categories on the basis of their chemical structure. They are:
1. Simple Carbohydrates
2. Complex Carbohydrates.
You can see in the image for further classification.
Carbohydrates, classification, functions, and examples of foods, composition of foods.
Classification of carbohydrates

Simple Carbohydrate

Simple carbohydrate consists of one or two single-sugar(saccharide) units or molecules. They provide an instant source of energy. Simple carbohydrate is divided into two categories. They are:
1. Monosaccharides: Mono means single and sacchar means sugar or simple sugar. Monosaccharides are the simplest carbohydrates which are composed of only one sugar unit that cannot be further broken down into simpler sugars. It is the simplest form of carbohydrates. Example of monosaccharides is Glucose, fructose, and galactose. 

Function of Monosaccharide:
➝ It provides an instant source of energy. Human body consumes carbohydrates only in the form of monosaccharides. 
➝ Monosaccharides are non-essential nutrients which you do not get them from the food. Your body can produce all the types of monosaccharides from other nutrients for proper functioning.

Examples of foods that contain free Monosaccharides:
➝ Fruits and fruit juices(glucose, fructose)
➝ Honey (glucose, fructose)
➝ Candies (glucose)
➝ Syrups: liquid glucose, corn syrup.
➝ Sweet wines: Soft drinks, energy drinks, chocolates etc.

➝ Glucose is also called dextrose. The molecular formula of glucose is C6H12O6.
➝ It provides an instant source of energy for all the body's activities. The primary function of glucose is to provide fuel for all the cells. All the cells in the body use the glucose to produce energy. 
➝ Glucose is present in honey, ripe fruits, soya drinks, Glucose powder, Grapes, Banana etc
➝ Glucose is absorbed in the small intestine mainly in the jejunum but also some amount in the duodenum, and ileum.  

➝ Fructose is the sweetest among naturally occurring sugar which is mainly found in the ripe fruits and honey. The molecular formula of fructose is C6H12O6 same as that of glucose.
➝ It is not essential nutrients which you do not need to get it from the food to be healthy. All the fructose produces in your body from glucose.
➝ The limited amounts of fructose can be used directly for energy.
➝ Most of the fructose reaches the liver via the vein and is converted into glucose, lipid or lactate. Fructose also participates in the metabolism.
➝ Fructose is present in Pear juice, Apple juice, Mango, Honey, Watermelon, Grapes, Orange juice, Tomato etc.

➝ It is also simple sugar which is composed of the same element as glucose but has the only difference in the arrangement of atoms.
➝ Galactose is also not essential nutrients. It also produces in the human body from the glucose. 
➝ Galactose is mainly present in the fruits, vegetables, nuts, grains, meat, eggs, and milk

2. Disaccharides: Disaccharides consist of two monosaccharide molecules or units join together with the removal of a water molecule. The general formula of disaccharides is C12H22O11. Examples of the disaccharides are sucrose, lactose, and maltose. It also provides energy to the body but is not essential nutrients for getting from the food to be healthy. 


➝ Sucrose is disaccharides carbohydrates which consist of glucose, and fructose.
➝ It is a source of energy which is present in the Mango chutney, fruits, Ice cream, Coconut cream etc.


➝ Lactose is also called milk sugar and is composed of glucose and galactose linked by beta 1-4 glycosidic bond.
➝ The source of high lactose is milk, curd, yogurt, ice cream etc.
➝ Lactose is a source of energy.

➝ Maltose is a malt sugar which is composed of two glucose molecules connected with an alpha 1-4 glycosidic bond. 
➝ The source of maltose is Honey, Jelly candies, Grapes, Pizza, meat, vegetables etc.
➝ It also provides a source of energy. 

Complex Carbohydrates: Complex carbohydrates are composed of long chains of sugar molecules. They are mainly found in foods such as peas, kidney beans, whole grains, Apples, bananas, and vegetables. Both simple and complex carbohydrates are converted into glucose in the body. The complex carbohydrates foods give vitamins, minerals, and fibers which are essential for good health. Example of complex carbohydrates is Polysaccharides.

Polysaccharides: Poly means many and sacchar means sugar. Polysaccharides are complex carbohydrates which consist of 10 to 1ooo monosaccharides arranged in chains. The main example of polysaccharides is starch and glycogen.  

Final words:

We hope that this article will help you to know about the Carbohydrates, classification, functions, food, and composition of foods. We have covered almost all the important topics in this article.