The Fundamental Unit of Life

Introduction of cell

The introduction to cell began back in the year 1655 when a revolutionary observation was made by an English scientist Robert Hooke. 
In all the living beings, cells are the basic structural units. We can compare the presence of cells in our body to the bricks in a building. All the bricks are assembled to make a building. Similarly, all the cells are assembled to make the body of an organism. 
Thus, it is the basic structural and functional unit of life and all the organisms are made up of cells. The subcellular structures of the cell comprise of the plasma membrane, organelles and in some cases a nucleus as well. As for the size of the cell, it is variable and maybe anything from 1 to 100 micrometre.
Robert Hooke was examining a dried section of the cork tree using a crude light microscope. In this analysis, he observed multiple small chambers which he named the cells. 
The first theory was proposed by the German botanist Matthias Jacob Schleiden and the German physiologist Theodore Schwann in 1838. This theory was formalized in the year 1858 by the German researcher Rudolf Virchow by suggesting that all cells arise from pre-existing cells.

 

Cell Theory

•    The cell is the basic functional and structural unit of life. All the living organisms are composed of cells.
•    All cells are formed by the division of the already existing cells which in terms of biology means reproduction.       Every cell of our body comprises of genetic material which is passed down during the process.
•    All the basic physiological and chemical functions i.e. the growth, repair, movement, communication, immunity and digestions are performed inside the cells.
•    All the activities of the cell depend mainly on the activities of the subcellular structures that lie within the cell. These subcellular structures comprise of the plasma membrane, organelles and if present, the nucleus.

Types of Cells

Broadly, there are two key types of cells i.e., the Prokaryotic Cell and the Eukaryotic Cell. The difference between the two is defined mainly by the presence or the absence of the nuclear membrane.

  1. Prokaryotic Cell

 If a cell has a nuclear material without a nuclear membrane, then it is known as the prokaryotic cell, where ‘pro’ stands for primitive and ‘karyon’ stands for the nucleus. Some of the organisms that have prokaryotic cells include bacteria and the blue-green algae.

  1. Eukaryotic Cell

If a cell has a nuclear material with a nuclear membrane, then it is known as the Eukaryotic Cell, where ‘EU’ stands for true and ‘karyon’ stands for the nucleus. All the living organisms except bacteria and blue-green algae have Eukaryotic Cells.