Cell is smallest structural unit and functional unit of organism.

In this article we will discuss about cell. Let’s first speak about its discovery.

Discovery of cell

Discovery of Cell

In 1665, Robert Hooke used slice of cork made up of bark of oak tree, for his study. During his study, Hooke noticed something strange!!!. “the slice of cork have some structures similar to that of small chambers of honeycomb.” he called these chambers as a cell. It is taken from latin word cella which means a small room. Initially, he found that, cell is just an empty structure, as, he wasn’t able to see internal component present in it. This was because of low magnifying power of microscope. Later, in 1676, Anton van Leeuwenhoek, used an improved microscope, and concluded that, cell is composed of different structures called cell organelles .

Variety in cell number

After confirmation of idea, it was clear that, each and every organism is composed of cell. However, different organisms have different number of cells. For example Amoeba, Paramoecium, Euglena have single cell. Such organisms are called unicellular organism. There are many other organisms such as human, animals and plants which have billions and trillions of cells. Such organisms are multicellular organisms.



A unicellular organism perform all the necessary functions such as digestion , respiration, excretion, growth and reproduction , similar to multicellular organism. The difference is unicellular organism have single cell to do all these activities whereas multicellular organism have dedicated organs to perform these activities. Note that a single cell i.e. fertilized egg divides and divides to form tissue. Different tissues form an organ for a specific function. Different organs, performing dedicated functions form a multicellular organism.

Shape of cells

Cells have different shapes. Some cells like amoeba, white blood cells can change their shape while others have definite shape e.g. paramoecium. The shape of a cells helps to perform specific function. e.g. Amoeba takes food inside the body using the two tall projections called pseudopodia, which disappear at the end of process. pseudo means false; and podia means feet. Paramoecium have cilia which help to move around in surrounding. Also it help to transfer food towards opening of mouth. Nerve cells in human beings have branches forming a network to send and receive signals between body parts and nervous system.

Size of cells

Like shape, cells may be of different sizes as well. Most of the cells are of micrometer size. The smallest cell is bacterial cell of size 0.1 to 0.5 micrometre. To view cells of such a small size there is need of microscope. There are few cells which could be as large as few centimeters. The largest cell is ostrich egg having size 17 cm × 13 cm.
Answer this ⟶ Between elephant and ant which one will have larger cell? Probably, you will say elephant. The size of the cells is independent of size of body of any organism. In fact the size of cell depends on function it is performing. e.g. in both elephant and ant the nerve cells are long and branched which perform the function of communication.

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Keywords: Cell organelle, Amoeba, Paramoecium, Euglena, Microscope

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