Carbon, oxygen, hydrogen, phosphorus, sulfur and nitrogen are the six elements that are responsible for the occupying 90% of the dry weight of the human body. The other elements that are found in the cells and also play the vital role are Ca, Zn, K, Cl, Mg, Cu, Co, Fe, Se, and Mo.

Biological molecules or Biomolecules are abundantly found in the body, with wide range of size and shape, performing variety of tasks. However, among the above described molecules the major one are carbohydrates, lipids, proteins and nucleic acids. These are non-living molecules and atoms, but are the essential one to carry the process of metabolism, reproduction, digestion, etc.


The most abundant organic molecules present in nature. As the name suggest it has the composition of the carbon, hydrogen and oxygen. Even when we break the name ‘carbohydrates’ it means hydrates of carbon. Carbohydrates are known as compounds that on hydrolysis produces polyhydroxy aldehyde or ketones. It is the chief dietary source of energy


Carbohydrate are the saccharides where sakcharon – sugar. and are broadly categorized under 3 category namely – monosaccharides, oligosaccharides and polysaccharides. This division or classification depends on the number of sugars units they have.

Functions of Carbohydrates

  • Carbohydrates act as the precursor of the numerous organic compounds such as amino acids, fats, etc.
  • These are most abundant and chief source of getting energy for all the organisms.
  • To fulfil the immediate energy demand of the body, carbohydrates act as the storage system of energy.
  • This molecule (carbohydrate) also participate in cellular activities such as adhesion, growth, fertilization and also present in cellular membrane.


Proteins are also one of the special class of molecules available in living being. They are responsible for the 50% of the body’s dry weight. They are responsible for the fundamental growth and functions of life.

Functions of proteins

Within the living cells proteins performs various specialized functions, which are categorized under two sections, those are the dynamic and the static or structural functions.


Structural functions – Proteins like collagen and elastin especially found in the bone matrix, and other organs are known to provide strength and structure of the body. Such proteins are play the roles of ‘brick and mortar’.

Dynamic functions – Even the key role of protein is acting as hormones, blood clotting factors, enzymes, immunoglobulins. This is the diversified nature of proteins performance, where it also supports in muscles contractions and relaxations, genetic control, storage proteins, respiration, digestion, etc. and therefore also popularly known as ‘the working horses’ of cell.

Nucleic acid

The genetic material present in the cell carrying hereditary information from the parent to their offspring is stored in the form of nucleic acids.

nucelic acid

The commonly known nucleic acids are the DNA and RNA. The DNA stands for deoxyribonucleic acids while RNA stands for ribonucleic acids.

Functions of Nucleic acid

  • First and foremost role of the nucleic acid is to participate in the function central dogma and to synthesize proteins for the body use. For the nucleic acid (DNA) completes the process of replication, followed by transcription and translation.
  • There are four main nitrogenous bases in DNA which are adenine, guanine, cytosine and thymine, while in case of RNA the thymine is replaced by the uracil and rest are same. These bases forms the structure of DNA and RNA. Therefore, the genetic material is transferred in the form of these nucleic acids.


The word Lipids has been derived from the Greek word ‘Lipos‘ which means ‘Fat’. The immense potential of storing energy and role in cellular structure, etc. makes it worthy. These are small molecules s compared to the protein, carbohydrates and insoluble in water, though soluble in organic solvents (ether, alcohol, etc.).

Functions of lipids

  • They are key source of fat soluble vitamins like A,D, E and K.
  • Lipids are vital cellular metabolic regulators working as steroid hormones and prostaglandins
  • Importantly they are the fuel reserve of the body like the triglycerols.

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