Explain Cell - The Basic Unit of Life

You must be aware of the fact that the cell is the basic unit of life. What do you understand by the term 'cell'? What are the components of the cell, its structural features and functions that make it such an essential component of all the living beings? Well, here in this section, we shall study about all these aspects related to cell. What would be the answer to the question what is a cell? Well, a cell is the smallest self-functioning unit found in all the living organisms. Cells may exist as independent units of life (as in monads) or may form colonies or tissues as in the higher plants and animals. Each cell is enclosed by an outer membrane or wall called as the cell membrane. A cell has receptors on its surface which have unique functions and identifying properties. Also, it contains genetic material (DNA) and other parts to carry out its life functions. Within the cell are the nucleus and the cytoplasm. The nucleus contains the genetic material-DNA.

The cytoplasm contains organelles that carry out the cell's functions. We shall read about these components of the cell in a little while from now. An aggregation of cells having a common origin and performing a similar but one or more specific functions in the body constitute a tissue (e.g. muscle). Several types of tissues may join collectively to form an organ that carries out one or more specific functions (e.g., kidney, liver, leaf and roots). In majority of animals, several organs are interrelated to perform a specific function within a multicellular organism and thus constitute an organ-system.

We will learn about this organ systems i.e. gastrointestinal system, renal system in the subsequent units. You would realize that several types of organ-systems in the body of an organism show unique example of division of labor. It is important to note that the cells are not only the building blocks of the body, but are the functional unit of life too. Every cell arises from pre-existing cells. The cells have the same genetic material. It is, therefore, capable of giving rise to a new individual. This potential of the cell to give rise to unlike cells and so to develop a new organism or a part is termed as totipotency. Interestingly, all the activities of an organism are present in miniature form in each and every cell. Therefore, the cell can be called as a basic unit of life and the structural unit of an organism. 'All organisms are composed of cells'. 'All cells come from pre- existing cells'. These two statements constitute the cell theory.