• Biomolecules, also known as biological molecules or macromolecules, are organic compounds that are found in living organisms.
  •  These molecules are the building blocks of life and are involved in the structure, function, and regulation of biological systems.
  • They are composed primarily of carbon (C), hydrogen (H), oxygen (O), nitrogen (N), and sometimes phosphorus (P) and sulfur (S).
  • Four main classes of biomolecules: carbohydrates, lipids, proteins, and nucleic acids.
  • Biomolecules interact with one another in complex ways to carry out various biological functions.
  • They form the basis for the chemical processes that allow living organisms to grow, reproduce, respond to their environment, and maintain their overall functioning.



How to Analyse Chemical Composition?


Analyzing the chemical composition of biomolecules using living tissue can be done through chemical analysis. Here are some steps to follow:


  1. Take a piece of living tissue and crush it.
  2. Mix the crushed tissue with an acid, such as trichloroacetic acid.
  3. After filtration, two portions can be obtained: the acid-soluble part and the acid-insoluble part.
  4. The acid-soluble part contains all the biomolecules present in the sample, while the acid-insoluble part has inorganic compounds like calcium, magnesium, sulfate, phosphate, etc..
  5. Analytical techniques can provide information about the different compounds in a tissue, including both organic and inorganic compounds, as well as their molecular formula and structure.
  6. To determine the chemical composition of an unknown biomolecule, one needs to determine the mass of the hydrogen, carbon, and oxygen present in it.


Primary and Secondary Metabolites

Primary and secondary metabolites are two types of biomolecules classified based on their role in cellular activities. Here are some points to understand the differences between primary and secondary metabolites with examples:

Primary Metabolites:

  • Involved in growth, development, and reproduction of the organism.
  • Essential for proper growth.
  • Formed during the growth phase as a result of energy metabolism.


    • Carbohydrates: These include glucose, a primary source of energy for cells.
    • Amino Acids: Building blocks of proteins, used in protein synthesis.
    • Nucleotides: Building blocks of DNA and RNA, critical for genetic information storage and transmission.
    • Lipids: Such as triglycerides, which are essential for energy storage and cell membrane structure.
    • ATP (Adenosine Triphosphate): The primary energy currency of cells, crucial for various cellular processes.

Functions: Primary metabolites play fundamental roles in energy production, growth, and cellular functions, and they are universally required by all living organisms.

Secondary Metabolites:

  • Organic compounds are produced through the modification of primary metabolite synthases.
  • Do not play a role in growth, development, and reproduction like primary metabolites.
  • Typically formed during the end or near the stationary phase of growth.
  • Many of the identified secondary metabolites have a role in ecological function, including defense mechanism(s), by serving as antibiotics and by producing pigments.


  • Phytochemicals: Secondary metabolites produced by plants, including alkaloids (e.g., caffeine), flavonoids, and tannins. They often serve as defense mechanisms against herbivores and have roles in plant-microbe interactions.
  • Antibiotics: Secondary metabolites produced by microorganisms and fungi, such as penicillin. They inhibit the growth of other microorganisms and are important in medicine.
  • Terpenoids: A diverse group of secondary metabolites that includes essential oils, steroids, and pigments. They have roles in plant protection and communication.
  • Polyphenols: Compounds like resveratrol (found in grapes) and quercetin (found in fruits and vegetables) have antioxidant properties and potential health benefits.
  • Toxins and Allelochemicals: Secondary metabolites can act as toxins or allelochemicals, affecting the growth and behavior of other organisms.

Functions: Secondary metabolites often have specialized roles, including defense against herbivores, signaling, and interactions with the environment. They are not universally required for basic life processes but are crucial for adaptation and ecological relationships.


Nature of Bond Linking Monomer in Polymer


In biomolecules, the nature of the bond linking monomers to form polymers typically involves covalent bonds. These covalent bonds are critical for the structural integrity and function of biomolecules. The specific type of covalent bond may vary depending on the type of biomolecule, but they all involve the sharing of electrons between atoms. Here are the common types of covalent bonds linking monomers in various biomolecules:


  1. Proteins:

    • Monomers: Amino acids.
    • Bond Type: Peptide Bonds.
    • Description: Amino acids are linked together by peptide bonds. These covalent bonds form between the amino group (-NH2) of one amino acid and the carboxyl group (-COOH) of another. The result is a covalent bond between the nitrogen and carbon atoms, with the elimination of a water molecule (condensation reaction).
  2. Carbohydrates:

    • Monomers: Monosaccharides (e.g., glucose, fructose).
    • Bond Type: Glycosidic Bonds.
    • Description: Monosaccharides are linked together through glycosidic bonds. These bonds form when the hydroxyl (-OH) groups of two monosaccharides react, resulting in a covalent bond between the carbon atoms of the monosaccharides. For example, in the disaccharide sucrose, a glycosidic bond forms between glucose and fructose.
  3. Nucleic Acids (DNA and RNA):

    • Monomers: Nucleotides.
    • Bond Type: Phosphodiester Bonds.
    • Description: Nucleotides are linked together by phosphodiester bonds. In this case, a covalent bond forms between the phosphate group and the sugar (ribose or deoxyribose) of adjacent nucleotides. This bond is essential for the linear structure of the nucleic acid and the genetic information it carries.
  4. Lipids (Triglycerides):

    • Monomers: Glycerol and fatty acids.
    • Bond Type: Ester Bonds.
    • Description: Triglycerides, a type of lipid, are formed through ester bonds between a glycerol molecule and three fatty acid molecules. These covalent bonds are important for energy storage in the form of fat.