Define cell and explain cell theory.

A cell is the smallest structural and functional unit of life capable of carrying out all vital biological processes.

Cell theory is a fundamental concept in biology that explains the properties and origin of cells. It consists of three main principles:

All living organisms are composed of one or more cells. This means that cells are the basic building blocks of all life forms.

The cell is the basic unit of structure and function in living organisms. All physiological activities occur within cells.

All cells arise from pre-existing cells through cell division. New cells are formed by the division of existing cells.

Cell theory establishes that life is cellular in nature and that cells are essential for the existence and continuity of life.