What is the respective importance of water, carbon and nitrogen for living beings?
Water is the major solvent of living beings and it is essential practically for all biochemical reactions, including as reagent of photosynthesis. Lots of properties of water are very significant for life.
Carbon is the major chemical element of organic molecules; carbon dioxide is also reagent of photosynthesis and product of the energetic metabolism of living beings.
Nitrogen is a fundamental chemical element of amino acids, the building blocks of proteins that in their turn are the major functional molecules of living beings; nitrogen is also part of the nucleic acid molecules, the basis of reproduction, heredity and protein synthesis.