Carbohydrates -Meaning, classification, examples, functions and 4 sources of Carbohydrates


Carbohydrates -Meaning, classification, examples, functions and sources of Carbohydrates


Carbohydrates are macronutrient comprising of carbon, hydrogen and oxygen at a chemical level. They are one of the ways by which our body obtain energy. Carbohydrates are found in fruits, grains, vegetables and other dairy products.

The body converts food that contains these carbohydrates into blood sugar or glucose when it is undergoing digestion in the digestive system. Carbohydrates are very common organic substances and very abundant in nature.

Carbohydrates are very important in living things. Substances such as starch, linen and wood were found to contain molecules of hydrogen (H), carbon (C), and oxygen (O), with a general formula of Cx(H2O)y for organic compounds. Carbohydrate is gotten from the French word “hydrate de Carbone” meaning water carbon or “hydrate of carbon”.

Classification and Examples of Carbohydrates

Carbohydrates are generally classified as monosaccharides, disaccharides, oligosaccharides and polysaccharides. Some of these monosaccharides which are also referred to as simple sugars are contained in fruits like grapes and honey.


Monosaccharides otherwise called simple sugar, is a combination of sugar and the simplest form of sugar and also the fundamental units of Carbohydrates. They cannot undergo hydrolysis to form simpler chemical compounds. They are generally crystalline solids which are colourless and soluble in water.

Worthy of note is the fact that not all compounds that fit into the general formula (CnH2On) for Carbohydrates, are Carbohydrates. The percentage of sugar and concentrated solution in monosaccharides is 50% respectively. The glucose of monosaccharides is very instrumental during metabolism, where chemical energy is removed as the Carbohydrates undergoes glycolysis.

They don’t need any special process to be broken down, unlike other Carbohydrates that require catalysts. As such when taken into the body as foods, monosaccharides go straight to the blood stream thereby increasing the blood sugar level in the body and immediately provide the body with the needed energy.

Examples of monosaccharides

• Glucose
• Fructose
• Glyceraldehyde


A disaccharide is formed when two simple sugars are linked together by a glycoside. Disaccharides, like monosaccharides, are simple sugars which can be dissolved in water. All the types of disaccharides each have a total of twelve carbon atoms with the general formula being C12H22O11.

The fusion of monosaccharides into disaccharides or double sugar is made possible through a process called condensation reaction which has to do with the expulsion of water molecules from the functional groups only.

The disintegration of disaccharides into the two corresponding monosaccharides could be achieved only through a process called Hydrolysis in the presence of an enzyme called disaccharidase. As water molecules get eliminated during the build-up of complex sugar, the breaking apart of the sugar also, in turn, consumes large molecules of water.

These reactions are very important during metabolism.

Examples of disaccharides

• Sucrose
• Maltose
• Lactose


Polysaccharides are also known as polycarbohydrate and are among the classes of Carbohydrates that are present in great quantity in the food we eat. The straight long-chain polymers of Carbohydrates which are composed of fragments of monosaccharides are joined together by glycosidic linkages.

In the presence of and enzyme called amylase which acts as a catalyst, polysaccharides are able to undergo hydrolysis, there by producing component sugars such as oligosaccharides or monosaccharides.
Polysaccharides vary in structure from linear to branches.

Examples of Polysaccharides

• Galactogen
• Cellulose
• Glycogen
• Starch
• Chitin


Oligosaccharide is a polymer of Carbohydrate which contains a moderate number of monosaccharides, usually 3-10. They function as cell adhesives and recognition. Oligosaccharides are further divided into two parts namely;
1.N-linked oligosaccharide (where the Olisaccharide is attached to asparagine remains by a beta linkage.
2.O-linked oligosaccharide (where the oligosaccharide attaches itself to serine or threonine of a protein.

Examples of Oligosaccharide

• Galactose

Functions of Carbohydrates

Carbohydrates function mainly as energy and food providers to the body and nervous system.
They play a pivotal role during metabolic processes.
They also prevent the breakdown of proteins for energy since they are the primary sources of energy in the body.

Sources of Carbohydrates

1.Simple sugars or monosaccharides are found in the form of fructose in many fruits.

2.All dairy products contain Galactose.
Lactose is excessively found in milk and other dairy products.
3.Maltose is present in processed cheese, beer, cereal, pasta, etc.
4.Sucrose is naturally obtained from sugar and honey containing small amounts of vitamins and minerals.

Thank you for reading to this point. Do you have a question or an addition to the information above? Kindly use the comment box below.


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