Molecules are lifeless. Yet, in appropriate complexity and number, molecules
compose living things. These living systems are distinct from the inanimate
world because they have certain extraordinary properties. They can grow, move,
perform the incredible chemistry of metabolism, respond to stimuli from the
environment, and, most significantly, replicate themselves with exceptional
fidelity. The complex structure and behavior of living organisms veil the basic
truth that their molecular constitution can be described and understood. The
chemistry of the living cell resembles the chemistry of organic reactions.
“Swamp Animals and Birds on the River Gambia,” c. 1912 by Harry
Hamilton Johnston (1858–1927). (Royal Geographical Society, London/The
Bridgeman Art Library.)
Indeed, cellular constituents or biomolecules must conform to the chemical
and physical principles that govern all matter. Despite the spectacular diversity
of life, the intricacy of biological structures, and the complexity of vital mechanisms,
life functions are ultimately interpretable in chemical terms. Chemistry
is the logic of biological phenomena.