Cell is defined as the structural and functional unit of the living body. All the living things are composed of cells. A single cell is smallest unit that has all the characteristics of life.

The general characteristics of most of the cells under normal conditions are:

  1. Cell needs nutrition and oxygen.
  2. It produces its own energy necessary for its growth, activities, and repair.
  3. It eliminates carbon dioxide and other metabolic wastes.
  4. It maintains the medium, i.e. the environment for its survival.
  5. It shows immediate response to the entrance of invaders like bacteria or toxic substances into the body.
  6. It reproduces by division. There are some exceptions like neuron, which do not reproduce.