Previous Year Question

Among the given alternatives, carbon, hydrogen and nitrogen constitute the best set directly associated with the formation of early organic molecules and the fundamental biomolecules of life.

Carbon: Carbon can form four covalent bonds and produce long chains, branched structures and rings. It therefore provides the structural framework for complex biomolecules such as carbohydrates, lipids, proteins and nucleic acids.

Hydrogen: Hydrogen is an important constituent of water and almost all organic compounds. It participates in the structures of biomolecules, hydrogen bonding, acid-base reactions and cellular energy transfer.

Nitrogen: Nitrogen is a major constituent of amino acids and proteins as well as the nitrogenous bases of DNA and RNA. It is therefore essential for both genetic information and protein formation.

Experiments and studies concerning early Earth have demonstrated the possibility of the abiotic formation of organic molecules, including amino acids, from methane, ammonia, water and other simple compounds. Carbon, hydrogen and nitrogen are prominent constituents of these molecules.

Scientific qualification: These three elements alone are not sufficient for present-day life. The principal elements required by known life are commonly represented as CHNOPS—carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur. However, among the four alternatives given in the question, option (b) most appropriately represents the organic basis associated with the origin of life.

Therefore, the correct answer is (b) Carbon, hydrogen and nitrogen.