Cell biology

DNA replication

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                              The Cell            

                Cell is nothing but structural and functional unit of life. Cell is very complicated structure where nucleus, mitochondria, ribosomes, cytoskeleton, smooth endoplasmic reticulum, rought endoplasmic reticulum and cell wall is present. Mostly this structures are present in eukaryotic cells while prokaryotic  cell structure is very simple.Cell was first discovered by Robert Hooke in year 1665.Cell is very tiny that is microscopic structure and microscope is needed to see it.  There are verious types of cells prsent in eukaryoteslike Nerve cell,Blood cells,Bone cell, Stem cells,Ovum, Sperm cell, smooth muscle cell and fat cells. 

                 Cell consists of various organelles this organelles are required for proper functioning of cells. This organelles are as follows

Plasma membrane:-

                   Eukaryotic cell is enveloped by cell membrane or plasma membrane in Animals while Plant cells also contain cell wall.In plant cell this plasma membrane is trilayered while in animal cell it is bilayered.This plasma membrane consists of Lipids therefor it is also called as lipid bilayer.Some proteins are present on lipid bilayer called Lipoproteins.This are either imbeded or Float on bilayer.This cell membrane also contain cholesterol in its Structure.Plasma membrane is responsible for gaseous transfer and oxygen as well as water and nutrient transfer inside the cell.

Nucleus:-

                  Nucleus is surrounded by double layered membrane known as Nuclear membrane.This nuclear membrane is consists of pores which allows transfer of m-RNA from inside to out side of nucleus as well as other components.This nucleus contains highly compact super coiled form of DNA in chromosomes.Histone proteins and DNA is main component of chromosomes.On the basis of presence of nucleus cells are of two types prokaryotic cell and Eukaryotic cell.Eukaryotic cell contains Nucleus while Prokaryotic cell does not contain nucleus.

Cytoplasm:-

                     Cyto means cell while plasma means matrix of Fluid. This matrix of fluid present inside cell in which various organelles are pesent.This cytoplasm contains network of fibres that help to maintain its structure. It contains cytosol in this matrix. Therefor cell has perticular fixed shape and cytosol present consists of glucose, nucleotides, minerals , Vitamins in it.

Endoplasmic reticulum:-

                     Inside cell a network of membranes is present known as Endoplasmic reticulum.Depending on the presence of ribosomes it is of two types SER and RER.SER refers to smooth endoplasmic reticulum which contain plasma membrane while ribosomes are absent.RER refers to Rough endoplasmic reticulum which contain ribosomes on its plasma membrane, This rough endolasmic reticulum is responsible for translation i.e. formation of protein from m-RNA and ribosomes and tRNA.

Golgi apparatus:-

                      Camello Golgi first identified this structure therefor it is called as Golgi apparatus.It contains cisternae which are closed, fluid filled flattened membranous sacs or vesicles. It is involved in Post translational modification of proteins.It contain proteins which modify other Preproteins into their actual fuctional form , modifing proteins ared known as Chaperons.

Lysosomes:-

                       This are responsible for death of cell when signals of this type transitted properly.They maintain different hydrolytic enzymes,proteolytic enzymes and have pH around 5. This means that are acidic in nature.They are responsible for digestion of cell organelles and busting of it causes Apoptosis

or self digestion i.e. cell death.

Cytoplasmic vacuoles:-

                           This are fluid, water and organic chemicals and biomolecules filled sacs.They acts as store house of cells.

Peroxisomes:-

                            They contain hydrogen peroxide molecules in it.Chemical formula of them is H2O2.

This peroxides are responsible for oxidation or Detoxification of Toxins,

Mitochondria:-

                          They are also called as power house of cell . There main fuction is generation of ATP or ATP synthesis.Krebs cycle is performed in mitochondria only.Mitochondria also contain DNA inside it which is mitochondrial DNA or Cytoplasmic DNA i.e. non-nuclear DNA.

Ribosomes:-

                         Ribosomes are particles consists of RNA and protein in equal amount.This are consists of two subunits small and large one.This ribosomes contain three types of RNA moleculkes i.e. 5.8s rRNA, 28s rRNA and 5s rRNA.This are atached to Rough endoplasmic reticulum and is responsible for formation of protein also called Protein synthesis.

Plastids:-

                      This occurs in plant cells. Chloroplast which is Green colored is a plastid. Chloroplast is green in colour because this absorbs all colours while emmits green colour.Chloroplast is responsible for Photosynthesis.Photosynthesis is formation of sugars and water from carbon dioxide and water with the help of sunlight and chloroform. Ths are mainly consists of Granna and Stroma.

So this is about the cell of Eukaryots.