Class 11 Biomolecules

5 minute read

Biology is an interesting subject as well as scoring. There are various branches of biology.  If you prepare well and are thorough with your notes, you can excel in the subject. Looking at the scope of biology, performing well in this subject can help you carve a career in it. Class 11 biomolecules is an interesting and important chapter in the biology syllabus. Here in this blog, we discuss in detail the various types and properties of biomolecules. If you are preparing for your class 11 exams then it would be of great help to you. Read on to know more about class 11 biomolecules. 

Must Read: CBSE Class 11 Biology Syllabus

What are Biomolecules?  

The chapter on class 11 biomolecules begins with first explaining what biomolecules are. Let us find out. 

  • Chemical molecules present in the living organism are known as biomolecules. Biomolecules can be further divided into two categories – i. organic ii. Inorganic.
  • Minerals, gases and water constitute inorganic molecules, whereas proteins, nucleic acids, carbohydrates and vitamins constitute organic molecules.
  • Based on chemical forms that biomolecules exist in, they can be further divided as ketones, aromatic compounds and aldehydes. Fatty acids, amino acids and nucleotides are forms of biochemicals.
  • All these macromolecules are formed by a process known as ‘polymerisation’ of monomers.
  •  Amino acids are linked by a peptide bond formed by the dehydration reaction between the carboxyl group of one amino acid and NH3 group of next with the subsequent removal of H2O. 
  • Like the peptide bond, there are two similar bonds known as phosphodiester bond and glycosidic bond.
  • Like peptide bonds,  Phosphodiester bonds involve the linking of 3’ C of sugar of one nucleotide to the 5’ C of sugar of next nucleosides with the subsequent releasing of two water molecules, in nucleic acids and glycosidic bonds are those bonds that link the monosaccharides of a polysaccharide through dehydration that takes place between two carbon atoms of adjacent monosaccharides.

Polysaccharides (Carbohydrates)

Next in class 11 biomolecules we move on to finding out what are polysaccharides. Polysaccharides are long chains of sugar formed by the subsequent attachment of monosaccharide units.

  • Starch: Present in plants as a storehouse of energy and forms a helical secondary structure.
  • Cellulose: Contains glucose molecules linked together by 1-4 β linkage. It is considered to be the most abundant organic molecule on earth.
  • Glycogen: It primarily acts as the reserve food materials for animals, bacteria and fungi and thus is also known as animal starch. 


Class 11 biomolecules also talk about proteins and their various qualities and properties. We have listed the important points below:

  • Polymers of amino acids that are linked by peptide bonds.
  • Formed by peptide linkage of 20 amino acids
  • There are two types of amino acids – a. essential amino acids – obtained from food and b. non-essential amino acids prepared by our body. 
  • Proteins are considered necessary for the human body to fight against infections, for enzyme production and transport of nutrients.

The three structures of proteins –

Class 11 Biomolecules
Image Source: NCBI-NIH

Nucleic Acids

Moving further in class 11 biomolecules, we study the properties and qualities of nucleic acids.

  • Nucleic acids are polynucleotides. It has three chemical components- a heterocyclic compound, a nitrogenous base, polysaccharides that are ribose/ deoxy-ribose sugar and phosphate or phosphoric acid.
  • The two types of sugar found in nucleic acid are ribose or deoxyribose. Nucleic acids containing deoxyribose sugar are called DNA and ribose sugars are called RNA. 


Class 11 biomolecules has a considerable part on metabolism and the many processes involved in it. We have described and defined metabolism for you below. 

  • In living beings, molecules are constantly being changed to some other molecules. This breaking and making process is known as metabolism. All these metabolic reactions are catalysed by enzymes.

Metabolic Pathways 

Metabolic pathways are an important part of the process of metabolism. It is discussed in class 11 biomolecules. 

  • Anabolic pathways are pathways that lead to complex structure formation from simpler ones. Examples of anabolic pathway – Photosynthesis and protein synthesis
  • Catabolic pathways lead to the formation of simpler molecules from complex molecules. Examples of catabolic pathway – Respiration and digestion
  • ATP or Adenosine Triphosphate is the energy currency of the living world.


Moving further in class 11 biomolecules we find out what are enzymes and what are their properties. 

  • Commonly known as biocatalyst.
  • Are proteinaceous substances capable of catalysing chemical reactions of biological origin without themselves undergoing any change
  • Enzymes, however, get damaged at high temperatures. Enzymes isolated from thermophilic organisms (live under high temperatures) are thermostable.
  • Enzymes are responsible for lowering the activation energy of reactions.
  • The formation of the ES (Enzyme Substrate) complex is essential for catalysis.

                                       E + S   ES →EP →E + P

(structure of substrate gets transformed into the structure of product through formation of transient state structure)

  • The point of difference between inorganic and organic catalyst that is enzyme is that inorganic catalyst works effectively at high temperature and pressure but enzyme get damaged at high temperature.
  • The external energy required to start a chemical reaction is called activation energy.

Factors Influencing Enzyme Activity

Next in class 11 biomolecules, we discuss the many factors which influence enzyme activity. Let us find out.

  • Enzyme actions happen within a narrow range of temperature. Temperature at which enzyme activity is the highest is known as optimum temperature. Activity increases and decreases both above and below that temperature.
  • Enzyme actions have an optimum pH at which it is maximum active.
  • Concentration of Substrate– With the increase in substrate concentration the rate of reaction increases due to occupation of more active sites by substrate.

There are certain compounds known as competitive inhibitors, the molecular structure of the inhibitor resembles the substrate, and inhibits the function of enzymes.

Classification of Enzymes

Moving further in class 11 biomolecules, we discuss the classification of enzymes. They are mentioned below:

  • Oxidoreductase/dehydrogenases: Catalyse oxidoreduction between 2 sub- strates.
  • Transferases: Catalyse transfer of a group between a pair of substrates.
  • Hydrolases: Catalyse hydrolysis of ester, ether, peptide, glycosidic, C-C, P-N bonds.
  • Lyases: Catalyse removal of groups from substrates by mechanisms other than hydrolysis.
  • Isomerases: Catalyse inter-conversion of optical, geometric or positional isomers.
  • Ligases: Catalyse linking together of 2 compounds.

What are Cofactors?

Towards the end in class 11 biomolecules, we find out what are cofactors. Non protein compounds are found attached to the enzymes to make it catalytically active. The protein component is known as apoenzyme.

  • Organic compounds that are tightly bound to apoenzyme are known as prosthetic groups. E.g., haem in peroxidase and catalase.
  • Coenzymes are those organic compounds which have transient association with enzymes.
  • Metal ions are generally required for enzyme activity and they form coordination bonds with side chains at the active site and with substrate.

Explore: NCERT Biology Class 11

So, this was all about class 11 biomolecules. Choosing the right stream after class 12th is important and further paves the way for your bright future. If you need guidance about what to pursue after class 12th, get in touch with our Leverage Edu experts. They will guide you every step of the way. Sign up for a free session today! 

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