What is the smallest unit of life?

What is the smallest unit of life?

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

Answer: (D)

The key idea is what can carry out all life processes. A cell is the smallest unit that can perform the essential functions of life—metabolism, growth, responding to the environment, and reproduction—within its own boundaries. Atoms and molecules are the building blocks that make up matter and organisms, but by themselves they don’t exhibit the coordinated activities that define life. An organism can be as simple as a single cell or as complex as many cells working together, yet the unit capable of carrying out life processes on its own is the cell. In single-celled organisms, one cell does everything; in multicellular organisms, many cells specialize and cooperate, but the fundamental living unit remains the cell.

The key idea is what can carry out all life processes. A cell is the smallest unit that can perform the essential functions of life—metabolism, growth, responding to the environment, and reproduction—within its own boundaries. Atoms and molecules are the building blocks that make up matter and organisms, but by themselves they don’t exhibit the coordinated activities that define life. An organism can be as simple as a single cell or as complex as many cells working together, yet the unit capable of carrying out life processes on its own is the cell. In single-celled organisms, one cell does everything; in multicellular organisms, many cells specialize and cooperate, but the fundamental living unit remains the cell.