The basic unit of life

• A. Atom
• B. Molecule
• C. Cell
• D. Organ

Answer: (C)

The basic unit of life is the cell. This means life processes occur inside cells, and a cell is the smallest structure capable of carrying out the functions that define living systems. Cells have a boundary membrane and internal structures that carry out metabolism, growth, and reproduction, all organized around genetic material. This idea is captured by cell theory: all living things are made of cells, and new cells arise from existing cells. Atoms are the building blocks of matter, and molecules are groups of atoms that form the chemicals of life, but they don’t by themselves perform life processes. An organ is a higher level of organization—tissues working together—rather than a basic unit of life. (Viruses are sometimes discussed in this context, but they are not cells and don’t carry out life processes on their own.)