The most abundant compound in most living things is water (H2O).
Water is essential for life and constitutes a large percentage of the mass of living cells. It plays a crucial role in various biological processes, including metabolism, temperature regulation, and nutrient transportation. Approximately 70% of the human body and around 90% of the composition of many plants is made up of water. Its unique properties, such as high specific heat capacity, solvent abilities, and its role in chemical reactions, make it indispensable for sustaining life. Thus, it’s clear why water is considered the most abundant compound in living organisms.