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LYSOSOME

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LYSOSOMES:-               They were discovered accidentally by a Belgian scientist,Christian de Dive,in 1955 through fracionantion technique.          Lysosomes are small vessicles which are bounded by a single membrane and contain hydrolytic enzymes in the form of minute crystalline or semicristaline granules of 5-8 nm. About 50 enzymes have been recorded to occur in them. All the enzymes Do not occur in the same lysosome but there are different sets of enzymes in different types of Lysosomes. The important enzymes are acid phosphatases, sulphatases,p peptidases,nucleases,lipases and carbohydrases. They are also called acid hydrolases because these digestive enzymes usually function in acidic medium or pH of 4-5. Acidic conditions are maintained inside the Lysosomes by pumping of H+ or proton into them. The covering membrane of Lysosomes keep the hydrolytic enzymes out of contact from cellular contents. Lysosomes are called suiside bags because of the presence of a large number o
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GOLGI COMPLEX

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GOLGI COMPLEX / GOLGI APPARATUS:-              Golgicomplex is a complex cytoplasmic structure made up of smooth membrane saccules or Cisternae,a network of tubule with vesicles and vacuoles ,which takes part in membrane transfermation, secretion and production of complex biochemicals. It is sorrounded by an organelle free cytoplasm called zone of exclusion or golgi ground substances.   Occurance:-  Golgi apparatus or complex is absent in prokaryotic cell. It is present in all eukaryotic cells except sieve tubes of plants ,sperms of bryophyte and pteridophytes and red blood corpuscles of mammals.  Location:-  In animalcell Golgi complex is either single or consists of a single connected complex. The two condition are respectively called localised and diffused . The localised organelle is compact. It generally occurs at one end between the nucleus and the periphery . The diffused organelle is found to from a network , e.g., around the nucleus in nerve cells. STRUCTURE OF GOLGI
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ENDOPLASMIC RETICULUM

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ENDOPLASMIC RETICULUM:-          It was discovered independently by "Porter(1945)and Thompson(1945). The name was given by "Porter"in 1953. Endoplasmic reticulum is a 3-dimensional,complicated and inter-connected system of membrane - lined channels that run through the cytoplasm. At places ,it is connected with plasmalemma as well as nuclear envelope. Plasmodesmata contain in the form of desmotubules .Endoplasmic reticulum divides the intracellular space into two compartments luminal  and extraluminal.         Depending upon the nature of its membranes , endoplasmic reticulum is of two types  e.g. smooth Endoplasmic reticulum and rough Endoplasmic reticulum. SMOOTH ENDOPLASMIC RETICULUM:-                  It has smooth membranes which donot bear ribosomes.It is ,therefore also called agranular Endoplasmic reticulum. This type of ER is found in cells engaged in the synthesis and storage of glycogen,fat and sterols. It is also commonly found in leucocytes .Smooth
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Mitochondria

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MITOCHONDRIA:-               Mitochondria are cell organelles of aerobic eukaryotes which takepart in oxidative phosphorylation and Krebs cycle of aerobic respiration. They are called power House  of the cell because they are the major centres of release energy in the aerobic respiration. They were first observed by kolliker in 1880. Benda   gave the present name of mitochondria to the organelles. Mitochondria can be stained differentially with Janus green and are easily distinguishable under light microscope though ultrastructure can be studied only under electron microscope.               Mitochondria absent in prokaryotes and anaerobic eukaryotes. Mitochondria are secondarily lost in the red blood corpuscles of mammals. Their number varies from one to several. The number depends upon cellular activities. Cells of dormant seeds have very few mitochondria Those of germinating seed have several mitochondria. (Structure of mitochondria)          Commonly mitochondria are cyli
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NUCLEUS

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NUCLEUS:-        Nucleus is a specialized double membrane bound protoplasmic body which contains all the genetic information for controlling cellular metabolism and transmission to the posterity .A nuclues in the non-dividing or metabolic phase is called interphase nucleus .Like other cellular Structure s,living unstained nucleus doesn't show much internal differentiation.                 Nucleus is the largest cell organelle .Though first observed by Leeuwenhoek in red blood corpuscles of fish,nucleus was first study in orchid root cells by Robert brown in 1831.     NUMBER-- Commonly cells are "uninucleate" that is they posses a single nucleus. Binucleate- they posses two nuclei found in 'paramecium caudatum' Multinucleate- it is also known as polynucloid condition which are found in bone marrow, striated muscles,latex vessels etc.     Shape-- the nuclei are generally rounded in outline.They appear oval or elliptical In plant cell .Disc shape nuclei occ
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Covering of cell

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Cell covering :-       Generally eukaryotic cell is cover by 2 layer the outermost layer is known as cellwall and inner to the cellwall cellmembrane is present. So we will first discuss about cell wall and then cell membrane 1.CELL WALL:-           It is the outer rigid protective supportive and semitransparent covering of plant cells,fungi,and some protists.cell wall was first seen in " cork cell"  by Hooke  in 1665.its thickness varies in different types of cell from "0.1micrometer to 10micrometer".cell wall is a nonliving extracellular secretion or matrix of the cell which is closely appressed to it. It is metabolically active and is capable of growth.cell wall performs a number of functions like - (I). Protects the protoplasm against mechanical injury (II). protects the cell from attack of pathogens (III).provides rigidity and shape to the cell (IV).counteracts osmotic pressure (V).pits present in the wall help to produce a protoplasmic countinum
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Cell biology

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THE CELL:-            The cell is known to be the fundamental basic structural and functional unit of living organism .all living organism whether plants or animals are made-up of cells.the term cell was introduced by an English scientist "ROBERT HOOKE". cell is protoplast sorrounded by cell membrane .which is also known as plasma membrane.                                                            (Structure of animal cell) Cell theory:-         The cell theory was formulated by the two German scientists "Mathias schleiden and theodere Schwann" independently.they examined and observed a large variety of plant tissues and devised that all plants are composed of different kinds of cells.       The cell theory fail to explain how and from where the new cells were formed .all these observation leads to major expansion of cell theory that was expressed by RUDOLF VIRCHOW in 1855 modified the hypothesis of schleiden and Schwann and explained in his statement that
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