The basic organic unit of life is the CELL. Cells are the smallest unit of life that can exist independently and are made up of a variety of molecules, including proteins, carbohydrates, lipids, and nucleic acids. Cells are the building blocks of all living organisms, from single-celled bacteria to complex multicellular organisms like humans. Cells are responsible for many of the functions that keep us alive, such as respiration, digestion, and reproduction.