learn what is cell | human cell, definition, history, functions, types | Edumistic

 

What is cell ?

Definition :

Mass of cytoplasm externally bounded by cell membrane. It is structural ,functional unit of life. Cell may contain many organelles which perform many specific functions such as mitochondria, nucleus, ribosomes, endoplasmic reticulum, lysosomes, centriols etc. These organelles are discussed in next article.

All living things are composed of cell.

A cell also called a building block of life. It is because cell have a nucleus which is the central part of cell and contain chromosomes. These chromosomes contain genetic information which are necessity for reproduction. Basically we can say that cell have a self replicating ability that is why we called as building block of life.

Diagram of :  human cell

History of cell :

A British scientist Robert Hooke first discovered the cell. He used microscope to study the piece of cork. This piece of cork contain many tiny components like a Honey Comb. He first named as cell in 1965.      History

History of human Cell

After Robert Hooke a scientist Anton Van Leeuwenhoek lived in Holland used the modern microscope and discover many useful things about cell. He first time discover the Human cell and bacterial cell.

                               

                                       

                                  

Cell Theory : 

Early 1800s many scientist observed and discovered many cells of different living organisms.

Two German scientists Schleiden and Schwann proposed a statement about cell. They say that, “ cells are the building blocks of all living organisms.”

Another German scientist Rudolf Virchow described “the division of cell”.

All three scientists Schleiden, Schwann, and Virchow proposed the cell theory according to their observations. Cell theory have 3 main postulates.

They stated that;

• ·        All or organisms made of one or more cells.

• ·         All the functions of organisms life occurs with in the cell.

• ·         All cells come from already existing cells.

Types of cell :

There are two types of cell.

• Prokaryotic cell

• Eukaryotic cell

Difference between prokaryotic cell and Eukaryotic cell :

Prokaryotic cell	Eukaryotic cell
Prokaryotic cell have no true nucleus.	Eukaryotic cell have true nucleus
Contain one chromosome but not true plasmid.	More than one chromosomes are present
Prokaryotic cells are usually unicellular	They are multicellular
Example:Present in Cyanobacteria, Archaea	Present in animals and plants.
The cell wall is usually chemically complex	Cell wall is chemically simple and present only in plants and fungi
The size of prokaryotic cell is usually 1to 10 micrometer.	Eukaryotic cell size is usually 1 to 100 micrometer.

Difference between Plant cell and animal cell :

Plant cell	Animal cell
Plant cell contain a membrane like structure inside the cell membrane called as cell wall	Only cell membrane is present while cell wall is absent in case of animal cell.
Plant cell contain a cytoplasm which contain many organelles .	Small vacuoles are present which used to store food and transport of things.
Well defined nucleus is present	Animal cell have no proper shape
Plant cell have a specific shape	Plastics are absent in animal cell
Chloroplast containing chlorophyll is present in plant cell which provide colour to the plant	Cytoplasm is filled with a fluid which help the vacuoles movement