What is Biomolecules

“Practice isn't the thing you do once you're good. It's the thing you do that makes you good.” 
-  Malcolm Gladwell, 

Certain characteristics in a living organism such as growth, reproduction, ability to sense, respond, etc distinguish the organism from a non-living thing. It has always been mysterious that despite being made up of non-living molecules, how a living organism performs all the above functions which characterize life. In this chapter, we shall try to unravel this mystery with the study of biomolecules.


Biomolecules are the molecules present in a living organism.  These biomolecules are fundamental building blocks of living organisms as they support the biological processes essential for life. Eg carbohydrates, proteins, nucleic acids, lipids, vitamins, etc. Carbohydrates are involved in energy storage; the hormones catalyze the biochemical reactions; DNA/RNA store/transmit the genetic codes of a living being.

Besides, various techniques such as DNA fingerprinting is based on the study of the biomolecules and widely used in forensic laboratories for identification of criminals, determine paternity of an individual or in the research of biological evolution.

The inadequate concentration of these biomolecules shall lead to various kinds of health ailments. Therefore, the presence of biomolecules in appropriate concentrations is vital for the proper function of living beings.


















In this chapter, we shall focus on Carbohydrates, Proteins, Vitamins, Nucleic acids.


Notes for the Biomolecules

In this section, you will study about the important topics of the chapter, overview and some important tips & guidelines for the preparation of the chapter at the best.


Important Topics of Biomolecules

  • Structures of Monosaccharides and Disaccharides (Oligosaccharides)
  • Chemical reactions of Glucose
  • Amino Acids
  • Denaturation of Proteins
  • Classification of Vitamins
  • The biological function of Nucleic acids


Overview of Biomolecules


Carbohydrates: Carbohydrates are naturally occurring organic compounds. They are vital for life as they form a major portion of food. Also, Cellulose (a carbohydrate) is present in wood and cotton fibre. Chemically, Carbohydrates are optically active polyhydroxy aldehydes/ketones or substances which yield such products on hydrolysis. Their general formula is Cx(H2O)y.

They are also known as saccharides which are further categorized as:




Some common examples of Carbohydrates are Glucose, Fructose (Monosaccharides), Maltose, Lactose, Sucrose (Disaccharides), Starch Glycogen, Cellulose (Polysaccharides), etc.

  1. Monosaccharides: Monosaccharides are further classified on the basis of the functional group present in them. Monosaccharides containing an aldehyde group are known as aldoses whereas the monosaccharides with a keto group are known as ketoses.
  1. Glucose: One molecule of Glucose contains six carbon atoms and aldehydic group. It is the simplest and abundant carbohydrate (monosaccharide). It is also commonly known as blood sugar and dextrose. Most of the glucose consists of molecules shaped into hexagon ring.

















ii.Fructose: One molecule of Fructose contains six carbon atoms and a ketonic group. It is fruit sugar and simply known as ketonic monosaccharide found in many plants, where it is often bonded to glucose to form sucrose(a disaccharide).





   b. Disaccharides: Two monosaccharides units linked through an oxygen atom; Such linkage is called glycosidic linkage. Disaccharides on hydrolysis with dilute acids or enzymes yield two molecules of either the same or different monosaccharides.

i. Sucrose: Formed by condensation of one molecule of α–D-glucose and β-D-fructose each. Sucrose occurs naturally in plants, from which table sugar is refined. The molecular formula of sucrose is C_{12}H_{22}O_{11}


                  ii. Maltose: Formed by condensation of two molecules of α -D- glucose. Maltose is the result of enzymatic hydrolysis of amylose ( homopolysaccharide) by the enzyme amylase.



iii. Lactose: Commonly known as Milk sugar; Composed of one molecule of β –D-glucose and β-D-Galactose each.


Proteins: Proteins are polymers of α-amino acids. They are essential for growth and maintenance of a living being’s body. They occur naturally in milk, cheese, pulses, peanuts, fish, meat, etc.

Amino acids contain an amino (–NH2) and carboxyl (–COOH) functional groups. The amino acids can be classified as α, β, γ, δ and so on, on the basis of the relative position of the amino group with respect to the carboxyl group. Eg Glycine, Alanine, etc.

Amino AcidGlycine


Peptide bonds: Proteins are the polymer of amino acids. The linkage/bond between molecules of amino acids is known as Peptide bond. 

Denaturation of Proteins: Change in the biological activity of a protein due to change in the ambient temperature or pH level is knowns as denaturation of Proteins. Curdling of milk or coagulation of egg white on boiling is an example of denaturation of Proteins.

Vitamins: Vitamins are organic compounds which help perform vital biological functions for growth & maintenance of the body.  They are generally classified based on their solubility in water or fats.

  1. Water-soluble vitamins: Vitamin B-complex i.e., B1, B2, B5, B6, B12, and vitamin C are water-soluble vitamins. Water-soluble vitamins must be supplied regularly in
    diet because they are regularly excreted in urine and cannot be stored (except vitamin B12) in our body.
  2. Water insoluble vitamins: Vitamins A, D, E and K are water insoluble vitamins.

Nucleic Acid: Nucleic acids are polymers of nucleotides present in the nucleus of all living cells. They play an important role in the biosynthesis of proteins. Also, they store and transmit the genetic codes of a living being from the parent to its offspring. Mainly, there are two types of nucleic acids - deoxyribonucleic acid (DNA) and ribonucleic acid (RNA).

Nucleic Acid

  • DNA contains the deoxyribose sugar, while RNA contains the ribose sugar. The main and only difference between ribose and deoxyribose sugar is that ribose has one more -OH group than deoxyribose, which has -H attached to the second carbon in the ring.
  • DNA is double-stranded and RNA is a single-stranded molecule.
  • Base pairing in DNA and RNA  is slightly different as DNA uses the bases adenine, thymine, cytosine, and guanine and RNA uses the bases adenine, uracil, cytosine, and guanine.


How to prepare? - Biomolecules

  • This chapter is a part of Organic chemistry and one of the most scoring chapter.
  • To understand the concept in this chapter, the candidate must have functional literacy of functional groups and stereoisomers.
  • Revision before a couple of days from the final examination is advised to obtain maximum marks.


Prescribed Books

The candidate should finish first the class XII NCERT textbook and solve each and every example and unsolved question given in it. For chapter biomolecules, the candidate has to stick by NCERT book only. The aspirant must definitely solve the previous year papers. Mock tests are advised for a thorough comprehension of the subject matter.  Our platform will help you to provide with the variety of questions for deeper knowledge with the help of videos, articles and mock tests.


Chemistry Chapter- wise Notes for Engineering and Medical Exams

Chapters No.

Chapters Name

Chapter 1

Some basic concepts in chemistry

Chapter 2

States of matter

Chapter 3

Atomic Structure

Chapter 4


Chapter 5

Chemical Thermodynamics

Chapter 6


Chapter 7

Redox Reaction and Electrochemistry

Chapter 8

Chemical kinetics

Chapter 9

Surface Chemistry

Chapter 10

General Principle and processes of Isolation of metals

Chapter 11

Classification of Elements and Periodic table

Chapter 12 


Chapter 13

p- block Elements

Chapter 14 

s-block Elements (Alkali and Alkaline Earth Metals)

Chapter 15 

Chemical Bonding and Molecular Structure

Chapter 16


Chapter 17

Coordination Compounds

Chapter  18 

Environmental Chemistry

Chapter 19

Purification and Characterisation of Organic Compounds

Chapter 20

Some Basic Principles of Organic Chemistry

Chapter 21


Chapter 22

Organic Compounds containing Halogens

Chapter 23

Organic Compounds containing Oxygen

Chapter 24

Organic Compounds Containing Nitrogen

Chapter 25


Chapter 27

Chemistry in Everyday Life

Chapter 28

Principles Related to Practical Chemistry

Topics from Biomolecules

  • General introduction and importance of biomolecules ( JEE Main ) (3 concepts)
  • Carbohydrates - Classification: aldoses and ketoses; monosaccharides (glucose and fructose) and constituent monosaccharides of oligosacctiorides (sucrose, lactose and maltose). ( JEE Main ) (27 concepts)
  • Biological functions of nucleic acids. ( JEE Main ) (3 concepts)
  • Nucleic Acids - Chemical constitution of DNA and RNA ( JEE Main ) (3 concepts)
  • Proteins - Elementary Idea of a-amino acids, peptide bond, polypeptides; Proteins: primary, secondary, tertiary and quaternary structure (qualitative idea only), denaturation of proteins, enzymes. ( JEE Main ) (28 concepts)
  • Vitamins - Classification and functions. ( JEE Main ) (13 concepts)

Important Books for Biomolecules

  • Biomolecules Book
  • Biomolecules Book