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Carbohydrates : Definition, Classifications & FAQs

Jul 7, 2022


We may have encountered the term ‘Carbohydrates’ in many areas, especially in food and diet-planning articles. So, what are carbohydrates? What foods are carbohydrates?

Carbohydrates are composed of three main elements: carbon, hydrogen and oxygen. All these are present at their element levels. It is one of the three major sources from which a human body gets energy. Moreover, carbohydrates are considered essential nutrients that contain fibres, sugars and starches.


In this informative blog, we will discuss everything related to carbohydrates in detail while looking at other related terms and concepts.

Carbohydrates Definition

The word ‘Carbohydrate’ comes from the French term ‘hydrate de carbone’, which simply means ‘hydrate of carbon’.


A carbohydrate is a macronutrient element composed of three different elements inside it. They are:

  • Carbon
  • Hydrogen
  • Oxygen

Carbohydrates give the necessary daily energy to our bodies in the form of fibres, sugars and starches. We can find carbohydrates mainly in fruits, vegetables and grains. One can say that they are the common food groups which we use in our everyday life in order to stay healthy.


Food that consists of carbohydrates is converted into blood sugar or glucose while digestion occurs. This process occurs in our digestive system. The body uses sugar as an energy source that tissues, organs and cells can utilise. 

Furthermore, the remaining sugar or energy is stored in our livers. It is also being stored in our muscles, which we can use for daily activities such as walking, running, swimming, etc. 


Given below is the general formula of carbohydrates:

Cn H2 On


Classification of Carbohydrates

 Carbohydrates are generally classified into two:

This categorisation depends mainly on their polymerisation degree and chemical structure.


Simple Carbohydrates

Usually, simple carbohydrates are elements that consist of one or two sugar molecules. In this type of carbohydrate, molecules are easily digested and transformed quickly. It results in a rise in the levels of blood sugar.

Simple carbohydrates are found in the following foods types:

  • Refined sugars
  • Milk products
  • Fruits
  • Beer
  • Candies

These carbohydrates are referred to as empty calories because they do not contain minerals, fibres and vitamins.

Since plants are regarded as producers, they synthesise glucose (C6 H112 O6) with the help of raw materials such as water and carbon dioxide in the presence of sunlight. This process is known as photosynthesis, where solar energy is converted into chemical energy. Furthermore, primary consumers consume plants and take energy from them.

Simple carbohydrates are of three types; they are:

  • Monosaccharide
  • Disaccharides
  • Oligosaccharides
  1. Monosaccharide:

Monosaccharides’ other name is carbohydrate monomer. An ideal example of a monosaccharide is glucose. Also, other examples include fructose, galactose and mannose. The following picture provides details about the monosaccharide’s structural organisation:

Galactose and Glucose 1

A carbohydrate monomer is further divided into five depending on the no. of carbon atoms it has:

  • Trioses (C3 H6 O3): They consist of three carbon atoms per molecule. An example of trioses is glyceraldehyde.
  • Tetroses (C4 H6 O4): They have four carbon atoms for every molecule. An example of tetroses is erythrose.
  • Pentoses (C5 H10 O5): They contain five carbon atoms per molecule. An example of pentoses is ribose.
  • Hexoses (C6H12 O6): They contain six carbon atoms per molecule. Examples of hexoses are glucose and galactose.
  • Heptoses (C7 H14 O7): They consist of seven carbon atoms for each molecule. An example of heptoses is mannoheptulose.
  1. Disaccharides:

In simple words, we can say that usually, two monosaccharides combine to form a disaccharide. Some examples of disaccharides are maltose, lactose and sucrose.

The following is the structural representation of carbohydrates containing two monomers:

Galactose and Glucose.

  1. Oligosaccharides

When carbohydrates are formed by condensing 2 to 9 monomers, oligosaccharides are produced. Using this convention, we can say that heptoses, hexoses, pentoses, etc., are all oligosaccharides.

Complex Carbohydrates

Complex carbohydrates are the elements that contain two or more two sugar molecules. They are termed starchy foods. In comparison with simple carbohydrates, the molecules present in complex carbohydrates are digested and converted very slowly. One can find complex carbohydrates in beans, lentils, peas, peanuts, potatoes, whole-grain, cereals and bread.

Complex carbohydrates are known as polysaccharides because the polymerisation process forms them. It involves the polymerisation of huge amounts of monomers. Some ideal examples of polysaccharides include cellulose, glycogen, starch, etc. All these are capable of exhibiting extensive branching. They are all made of only glucose units and are termed homopolymers.

Given below are the structure representations of the same:

Starch, Glycogen, and Celllose.

  • Cellulose: Cellulose is a fibrous polysaccharide containing high tensile strength. It is a main structural component of a cell wall since cellulose is a structural carbohydrate. Cellulose is capable of forming a linear polymer, which is not the same in terms of glycogen and starch.
  • Starch: Starch is made of two components; amylopectin and amylose. In that, amylopectin can be seen as a branched chain, whereas amylose can form a linear chain.
  • Glycogen: The other name of glycogen is animal starch. Glycogen consists of a structure similar to starch, but the only difference is that glycogen has numerous extensive branching.

What foods are carbohydrates?

Carbohydrates are found in various food items. Therefore, there are an enormous amount of sources available for obtaining carbohydrates. The following are a few sources of carbohydrates:

  • Sucrose: It is a naturally obtained carbohydrate from honey and sugar. Sucrose consists of very small quantities of minerals and vitamins.
  • Maltose: It is a very common form of carbohydrates and is found in various meals, namely beer, processed cheese, pasta, potatoes and cereal.
  • Lactose: Lactose is one type of sugar composed of galactose and glucose. The main forms of lactose are milk and other dairy products.
  • Galactose: Usually, galactose is as sweet as sucrose and glucose. It is majorly seen in all dairy products.
  • Fructose: Fructose is just simple sugar. It is widely found in many fruits.

These are simple sugars commonly found in fruits, milk and vegetables. They usually consist of vitamins and minerals. Apart from that, various processed and refined foods such as white rice, sugar and white flour lack the fundamental nutrients. Therefore, they are called enriched. 

Moreover, it is considered healthy to consume carbohydrates, vitamins and various other organic nutrients in their organic forms.

Functions of Carbohydrates

Some of the functions of carbohydrates include:

  • The sole purpose of carbohydrates is to provide food and energy to the human body as well as to the nervous system. So, that is why we consume carbohydrates daily.
  • Carbohydrates are used in fat metabolism. Hence, they are capable of preventing ketosis.
  • One of the main functions of carbohydrates is that they help preserve muscles.
  • A good amount of carbohydrate intake could improve digestive health.
  • However, consuming excess carbohydrates can lead to diabetes and heart attacks.
  • Carbohydrates hinder protein breakdown since they are considered the primary energy source.
  • An enzyme called amylase helps in breaking down starch into glucose. It then ultimately leads to producing essential energy for metabolism.

Carbohydrate Foods

Even though carbohydrates have a lot of benefits, there are still some risks, just like every other food. Overconsumption of carbohydrates can lead to serious health issues. Carbohydrates are simply sugar contained with other nutrients. Hence, consuming too much sugar can result in an abnormal increase in calories. High calories lead to obesity, while low calories can cause malnutrition.

Furthermore, we must follow a balanced diet to maintain a happy and healthy lifestyle. One can now understand why dietitians stress this too much to their patients.

The following tabulation will provide the differences between bad and good carbohydrates:

Bad CarbohydratesGood Carbohydrates
Contain less amount of nutrients.Contains a high amount of nutrients.
Consist of high cholesterol and trans-fat.Consist of low cholesterol and trans-fat.
Contain high amounts of sodium and saturated fats.Contain low amounts of sodium and saturated fats.
They have high calories.They have low to moderate calories.
Examples: processed foods, sodas, pastries, white flour and rice.Example: fruits, vegetables, beans, whole grains and legumes.


To conclude, just like any other object or food, overconsumption leads to serious illnesses. So, from this article, we have understood what a carbohydrate is, carbohydrates definition, simple and complex carbohydrates, sources and examples of carbohydrates. 

From all these subtopics, we have gathered an overall idea of how and when to consume it, considering all the factors.

Frequently Asked Questions

1. What is a carbohydrate?

A carbohydrate is nothing but one type of macronutrient which we consume in order to do our day-to-day tasks. It is made of three main elements; carbon, hydrogen and oxygen. Carbohydrates are considered essential nutrients with the inclusion of fibres, starches and sugars.

2. What foods are carbohydrates?

There are numerous carbohydrate-rich foods in this world. Some may be composed of good carbohydrates while others may be bad carbohydrates. The following are the food items that contain carbohydrates:

  • French fries
  • Soda
  • Processed cereal
  • Pastries
  • Rice
  • Whole grain
  • Beans
  • Legumes
  • White flour
  • Fruits and vegetables

3. Give some examples of carbs.

  • Fructose
  • Glucose
  • Maltose
  • Galactose
  • Sucrose
  • Starch
  • Lactose
  • Chitin
  • Cellulose


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