The difference between living matter and non-living matter is primarily the complexity of the molecules involved. The smallest unit of living matter is the cell. The cellular activities are carried out by macromolecules with the capability of providing the functions of Motility, Energy storage, Structure, Specificity, Information storage, Catalysis, and Hydrophobicity. Because all organisms are composed of cells, it is helpful to understand what it means to say that a cell or an organism is alive. Instinctively, each of us knows when a plant, animal, or person is alive or dead.
Metabolism is the sum of all the chemical processes in a living organism.
Cells are able to extract energy from the environment to fuel the chemical reactions that they, need to grow and reproduce. Most bacteria utilize chemicals that are supplied by their environment, whether it be soil, water, or a human stomach. The ultimate source of energy for all plants and animals is sunlight, which can be used directly by all plants and indirectly by animals, who obtain energy by eating plants or other animals. As a result of utilization of energy and synthesis of new molecules, cells increase in size and weight. Cells and microorganisms reproduce, giving rise to two identical copies of themselves.