Whats is Cells ? Types of Cells with explanation

Cell is the small­est unit of liv­ing tis­sue and it is a struc­tur­al and func­tion­al unit of liv­ing things. Cell of dif­fer­ent tis­sue per­form dif­fer­ent func­tions. It may be flat­tened, cubi­cal, colum­nar, fusiform, pyra­mi­dal or flask shape. 

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Most cells are com­posed of pro­to­plasm : A mix­ture of car­bo­hy­drates, lipids,proteins,nucleic acids, inor­gan­ic salts,gases and between 70–80%water.

There are three major parts of cell:

1. Plas­ma Mem­brane: It forms the water bound­ry of the cell and sep­a­rate it from adja­cent cell and exter­nal environment.

It trans­ports the sub­stances into an out of the cell. Its thick­ness majors amount 70 Angstrom. 

2. Nucle­us: It is the largest struc­ture present almost in the cen­ter of cell. It is more or less spher­i­cal in shape. It con­tains most of the cells genet­ic mate­r­i­al, organ­ic and mul­ti­ple long lin­ear DNA mol­e­cules with a large vari­ety of proteins.

3. Cyto­plasm: It is the region line between the cell mem­brane and nucle­us. The cyto­plasm con­tains cell organelles like Endo­plas­mic retic­u­lum, mito­chon­dria, gol­gi bod­ies, lyso­somes, cen­tro­some and cen­tri­ole etc. 

A) Endo­plas­mic retic­u­lum: It con­sist of a sys­tem with inter­com­mu­ni­cat­ing mem­branes sacs and exist in two forms. 

1. Rough Endo­plas­mic reticulum: 

It con­tains ribo­somes. The ribo­somes are the sites of pro­tein synthesis. 

2. Smooth Endo­plas­mic retic­u­lum: They does not con­tains ribo­somes. This type of Endo­plas­mic retic­u­lum is con­sult with fat­ty acid and steroids. They store and release calcium. 

B) Ribo­somes: They appear as dense round­ed gran­ules lying sin­gle or in dense clus­ter in the cyto­plasm in the form of spi­rals or may be attached to endo­plas­mic retic­u­lum. They are com­posed of ribonu­cle­o­pro­tein and sites of pro­tein synthesis. 

C) Gol­gi bod­ies: This is a sys­tem of sac arranged as stock of coins and the cycles like Endo­plas­mic retic­u­lum but with no ribo­somes attached to it. They trans­fer mate­ri­als syn­the­sised by the ribo­somes at the endo­plas­mic retic­u­lum to the cell sur­face. The parts of gogli bod­ies that con­tains new­ly man­u­fac­tured mate­ri­als brokes away from the best part of it and pass towards the sur­face of cell at secre­tion granules.

D) Mito­chon­dria: They are rod like bod­ies bound­ed by a dou­ble lay­ered mem­brane. They occur in the cyto­plasm at vari­able num­bers about few hun­dred to few thou­sands. An out­er lay­er which is smooth and an inner lay­er fold­ed into fin­ger like struc­tures or tubules called cristea. Both these lay­ers in close a cen­tral cav­i­ty called matrix. The Mito­chon­dria are made up of pro­teins, phos­pho­lipids and some ribonu­cle­ic acid. They also con­tain some impor­tant enzymes sys­tems. The Mito­chon­dria pro­vide the meta­bol­ic ener­gy to the cell by gen­er­at­ing ATP( Adeno­sine tri phos­phate) there­fore Mito­chon­dria is also known as pow­er house of the cell.