Introduction of biomolecule and Carbohydrate and its function

By Anup Pokhrel

Introduction of biomolecule

The branch of science that deals with the study of the chemical composition of the living organism and also the various chemical changes take place within them is known as biochemistry.There is the various chemical reaction that takes place within the living organism are commonly referred as metabolism. The raw material that is needed for the metabolic changes are the organic molecule, however, the reaction takes place inside body differ from the reactions that take place in the laboratory. In the biological system, a reaction takes place at body temperature and also at ordinary pressure. This is made due to the possible by the presence of catalyst substance called enzymes. A living organ system consists of many complex lifeless organic substances combined together in a specific manner. This substance generally contains macromolecules called biomolecules. This substance themselves are collectively referred as biochemical. The metabolism , biomolecules and biochemical in the presence of the suitable catalyst called enzyme play an important role in the living system for regulation excretion, secretion and for other purposes.



The term carbohydrate denotes hydrate of carbon and can be represented as general formula Cx(H2O)y. These are called carbohydrate because they can be treated as the hydrate of carbon. It is the compound made up of carbon, hydrogen, and oxygen in which ratio of hydrogen and oxygen is same as that of water. Carbohydrate has lost significance because of the following two reason.

  1. However, all carbohydrate do not have Cx(H2O)y formula such as deoxyribose sugar C5H10O4 .
  2. Similarly, all compound heaving formula Cx(H2o)y is not a carbohydrate. For example acetic acid (C2H4O2).

Carbohydrate is also called saccharides due to their sweet taste. The term saccharides are derived from Sharon which means sweet in taste. But all carbohydrate are not sweet in taste. For example.

Cellulose, Starch.

The recent definition of carbohydrate is.

The polyhydroxy aldehyde or polyhydroxy ketone or compound which gives polyhydroxy aldehyde or polyhydroxy ketone on hydrolysis are called carbohydrate. For example. Glucose (C6H12O6), Fructose Sucrose (C12H22O11), Starch (C6H10O5)n etc.

Carbohydrate which contains aldehydic group is known as aldose whereas other containing ketonic group are known as ketoses.

Carbohydrate is synthesised by green plants from CO2 and h2O in the presence of sunlight. This process is known as photosynthesis.

Carbohydrate is classified into three main group. They are.

  1. Monosaccharide.
  2. Disaccharides.
  3. Oligosaccharide.
  4. Polysaccharide.


1. Monosaccharide.

The carbohydrate which cannot be hydrolyzed to simpler carbohydrate is called monosaccharide. They cannot be hydrolyzed into the smaller unit. Their general formula is Cx(H2O)y ., Monosaccharide which contains aldehydic group are known as aldose whereas other containing ketonic group are known as ketoses. For example, Glucose-Fructose. Glucose is aldose whereas fructose is ketoses. A monosaccharide is further termed as Trios, Tetrose, Pentose depending upon the number of carbon atom present on them. Ribose is an aldopentose.


Glucose is commonly known as aldohexose sugar. They abundantly occur in plants and animals. It is found in juices of fruit, saps of plants , blood and tissues of animals. It is the immediate source of energy for cellular reaction in the body such as tissue repair, muscle movements etc. The overall glucose present in the blood of adult is five to six grammes . This sufficient to supply energy for about fifteen minutes and is continuously replaced in the body. It occurs in two isomeric forms.

Structure of D(+) Glucose
Structure of D(+) Glucose


Fructose is a ketohexose which is present in honey and fruit juices. It is sweet among all the monosaccharides. It can be converted into glucose in the liver and intestine and hence, used in the body.

Structure of D(-) Fructose
Structure of D(-) Fructose

2. Disaccharides.

That carbohydrate which on hydrolysis yields two molecules of monosaccharide units is called as disaccharides. They are crystalline in nature, soluble in water and sweet in taste.Example. Sucrose, Lactose, and Maltose.

3. Oligosaccharide.

These are compound sugar that yields 2-10 molecules of monosaccharide on hydrolysis. According to the number of monosaccharide unit, it is divided into disaccharide, trisaccharide and tetrasaccharide and so on. Among them, the only disaccharide is important for carbohydrate metabolism. Other oligosaccharides are found to be associated with other biomolecules like proteins and lipid. For example maltose, lactose, Sucrose trehalose, etc.

4. Polysaccharide.

Carbohydrate which contains more than 10 monosaccharide unit on hydrolysis is called polysaccharide. Example Starch Cellulose, glycogen.

They are further classified on the basis of taste (Solubility).

On the basis of taste (Solubility).

They are classified into two types.

  1. Sugar
  2. Non-sugar.

1. Sugar.

Crystalline carbohydrate which is sweet in taste and soluble in water are called sugars.

They are again classified as.

  1. Reducing sugar.
  2. Non-reducing sugar.

Reducing sugar.

Sugar which can reduce Tollen’s reagent (ammonium silver nitrate solution) are called reducing sugar. Example. Glucose.

Non-reducing sugar.

Sugar which cannot reduce Tollens reagent is called non-reducing sugars.

2. Non-sugar.

Carbohydrate which is insoluble in water and has no sweet taste are called non-sugar example. Starch, cellulose etc.

The function of carbohydrate.

  1. Carbohydrate is the major source of the energy in the cell of all living beings.
  2. Glucose is immediate and universal source of enzymes 1 gm of glucose on complete oxidation give 4.1 Kcal energy.
  3. Carbohydrate serves as the storage form of food in animal and plants. Starch is storage form in plant and glycogen is storage form in animals.
  4. Some carbohydrate like hyaluronic acid serve as the lubricant of joint and found in synovial fluid.
  5. Heparin is a type of polysaccharide that prevents clotting of blood inside the blood vessel.
  6. Mucin is a carbohydrate that is found in mucus secretion. It helps in lubricants of the surface of a mucous membrane.
  7. Carbohydrate can bind with other biomolecules such as protein and lipid found glycoprotein and glycolipid respectively. These are important in body physiology.
  8. Some carbohydrate plays the structural role in many organisms such as cellulose in plants, chitin in the cell wall of fungi and exoskeleton of an insect.


Important Questions
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