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CELL: STRUCTURE AND FUNCTION

Cell was discovered by Robert Hook, while he was observing cork cell under microscope. The cell he observed was dead cell at it appeared like small rooms or somewhat similar to honeycomb so he gave the the name "cell". Cell is known as the structural and functional unit of body. Cell is known as the structural and functional unit of body. As our body is made of organ and organs are made of tissues and tissues are made cell. So, cell is known as the structural and functional of body. Robert hook compared the cell with bricks as it is the basic requirement for making house so in similar cell is the basic unit of body. Later further development in microscope with higher magnification Anton von leeuwenhook discoverd first living cell that is Paramecium and others several scientists did research in this area and discoverd different part of cell and their function.

Depending upon the number of cell in organism they are differentiated into unicellular and multicellular organism. Unicellular organism are single-celled organism which performs similar function that of a multicellular organism. Example of unicellular organism is Amoeba, Paramecium etc. Multicellular organism as name suggest are organism consisting of many cells. There are some cells which changes its shape. Amoeba changes its shape due to locomotion and capturing its pray. WBC in human body changes its shape constantly. But there is a difference between them which you can identify now. All cell are not having similar shape. Cells are present in different shape like spherical, branched and spindle. RBC are spherical in shape whereas nerve cell is having branched structure and muscle cell is having spindle shape. As cells are present in different shapes similarly cells are not of same size. The size of cell ranges from few millimeter to centimeter. Cells of Bacteria are smallest cell whereas Ostrich's egg is the largest cell. There is three basic parts of cell that is cell membrane, nucleus and cytoplasm. Cell wall is absent in animal cell and present in plant cell. As we know that plants are immovable so they need protection from external environmental factors such as heavy wind, rain etc. So they need cell wall as it protects the cell and provides support. Cell membrane:- It is membrane present at inner side of cell wall in plants and in animals it is outermost membrane. It is semipermeable membrane as it allows entry of some particles and exit of some particles. It helps in exchange of particles through it. Cell membrane consists of carbohydrate, proteins and lipids. Cytoplasm:- It is jelly like structure present inside cell membrane. It consists of cell organelles like golgi apparatus, nucleus,plastids, endoplasmic reticulum, mitochondria, lysosome and microbodies. Nucleus:- It is main part of cell as it control and coordinates the cell. It consists of genes which helps in passing the genetic information from parent to offspring. The bacic parts of nucleus are nuclear membrane, nuclear pore, nucleoplasm, nucleosome and chromatin material. There is formation of chromosome at the time of cell division in chromatin material. There are several cell organelles present in cell which performs different function. Ribosome present at endoplasmic reticulum helps in protein synthesis. Lysosme helps in digestion of unwanted material present in cell by dissolving it with helpf of certain digestive enzymes. Plastids are colourfull pigments present in cell. Chloroplast is green pigment in plant which helps in photosynthesis. Cells are of two types i.e., Plant cell and animal cell. Plant cell does not have lysosome and have plastids. Animal cell lacks wall and have lysosome and plastids are absent.