What is the basic unit of life?

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

Answer: (D)

The basic unit of life is the cell because it is the smallest structure that can carry out all the activities required for life. Cells perform metabolism, grow, respond to their environment, and reproduce. They contain the necessary machinery—DNA, ribosomes, membranes, and other components—that lets them carry out these processes.

This idea is summed up by cell theory: all living things are made of cells, and new cells arise from existing cells. Atoms and molecules are the building blocks that make up cells, while organs are larger assemblies of many cells that work together to perform specific functions in multicellular organisms. So, while atoms, molecules, and organs play essential roles in life, the smallest unit that can independently sustain life is the cell.