Question

Define a cell in brief?

Answer 1

The cell is the structuctral unit of life because it is the tiniest living unit which have life. Our body is made up of trillions of cells. A cell is the building block of life. And a cell is also known as Functional unit of life because it is capable for doing any functions of our body such as excretion, respiration, reproduction etc....

Answer 2

$\textbf{CELL}$


→ Cells are the structural and functional unit of life.

* All living organisms are made up of cell. That's why cell is known as structural unit of life.

* A single cell can perform all life functions with the help of it's components. Therefore it is known as functional unit of life.

→ Robert Hooke first discovered the cell in 1665.

* He prepared a thin slice of cork and observed it under self made microscope. He saw some box like structures which he named as cell.

→ Anton Von Leeuwenhoek first saw the living cell and also first describe the living cell.

→ Cells can replicate independently.

→ It contain hereditary information due to presence of nucleus or nucleoid.

→ All organisms are made up of cells. Organisms with single cells are known as unicellular organisms. And organisms with multiple cells are known as multicellular organisms.

→ Cells size ranges from 1 - 100 μm.

→ Mycoplasmas, is the shortest cell (0.3 μm) and ostrich egg and nerve cells are the largest cell.

→ Cells are in different shapes. Their shape vary with their function. They may be cuboid, thread like, disc like etc.

→ Cells are of two types namely; Eukaryotic an Prokayotic cells.

a) Eukaryotic cells :-

* These are generally large in size.

* Nuclear region is well defined and surrounded by a nuclear membrane.

* These are multicellular.

* Single chromosome are present.

* Member bound cell organelles are present such as mitochondria, endoplasmic reticulum, golgi appartus etc.

* DNA is linear.

* Cell divides by binary fission and budding.

* Ex :- Human beings, plants etc.

b) Prokayotic cells :-

* These are smaller in size.

* Nuclear region is not well defined and not surrounded by a nuclear membrane.

* These are unicellular.

* More than one chromosomes are present in it.

* Membrane bound cell organelles are absent such as mitochondria, endoplasmic reticulum, golgi appartus etc.

* DNA is circular.

* Cell divides by mitosis and meiosis.

* Ex :- Bacteria, blue-green algae etc.
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