Cell: The Unit of Life

What is Cell?

Cells are the basic building blocks of life. A cell is a membrane bound structure that contains the  fundamental molecules of life and of which all living things are made. Some time

a single cell functions as a complete organism such as bacteria and yeast. Many cells often grouped together and functions as a whole as in higher animals and plants. Hence a cell is the  fundamental structural and functional unit of life.

History of the discovery of Cell

Let’s go back to the year of 1665. On his work table, Robert Hooke, an English Scientist, was curiously observing a thin slice of cork with the help of his own simple microscope. What he observed under his microscope was a honey-comb like structure, he named These structures “Cell”. The word  “Cell” means a box, a compartment or an empty room. The structure that he observed was actually the empty spaces enclosed by the cell walls of the dead plant tissue called cork. So it was the Robert Hooke who first discovered the cell, more precisely the dead cells. 

Cell structure of cork by Hooke 

For the first time, a living cell was observed by an another Biologist named “ Anton Von-Lewvenhoek in the year 1674. He was the ‘father of microbiology’ and a Dutch biologist. One day, he was inspecting pond water under his own designed microscope and got surprised to see tiny motile creatures, he called them the ‘animalcules’. Animalcule is a Latin word meaning ‘little animals’. These were probably the Protozoans moving in the water drop. This was the first documented view of the micro-world that was hidden to the humans so far. Later he studied many other microscopic organisms and cells including bacteria, blood cells and sperms.

“Finally, the work of Schlieden and Schwan along with the significant contribution of Virchow, shaped the Modern Cell Theory”

In 1833, Robert Brown, best known for the discovery of random motion of microscopic particles which came to be called Brownian motion, discovered the nucleus while studying the epidermis of the orchid under a microscope.

Cell Theory 

Over a century later in the year 1838, Matthias Schleiden, a German botanist, studied plants and found that all plants are made up of cells that make up tissue. In 1839, after studying various plants and animals, the British zoologist Theodore Schwann observed that all plants and animals are made up of cells and that the animal cell was covered with a membrane that we today call the plasma membrane. Also he found that the plant cells have an extra outer layer called the cell wall and is a unique feature of plants.

Based on their studies on various plants and animals, Schleiden and Schwan together proposed the first cell theory as: 

“Bodies of Animals & Plants are composed of Cells and Products of cells”

The above theory didn’t talk about the origin of cell. In 1855, a German Biologist and Physician Rudolf Virchow based on his studies,  made a crucial modification in the old cell theory and completed it by adding his famous phrase : 

“ omnis cellula-e cellula”

Which means ‘Cells divide and new cells are formed from pre-existing cells’.

Finally, the work of Schlieden and Schwan along with the significant contribution of Virchow, shaped the Modern Cell Theory as stated below:

1. All living organisms are made up of cells and products of cells.

2. All cells arise from the pre-existing cells.

In a nutshell, “ Cell is the fundamental structural & functional unit of  all living organisms”

In the next blog we will discuss about the characteristics of cell.

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