Cell : The Unit of Life

Endomembrane system

  • The endomembrane system includes endoplasmic reticulum (ER) golgi complex, lysosomes and vacuoles.
  • ER is made up of three components : cisternae, vesicles and tubules.
  • ER is bound by a single membrane, is of two types RER (Rough Endoplasmic Reticulum) & smooth endoplasmic reticulum (SER).
  • RER bears ribosomes on their surface and SER appear smooth and doesn't contain ribosome on their surface.
  • Synthesis and secretion of specific proteins via golgi bodies is one of the function of ER.
  • ER helps in glycogenolysis in the liver cells and brings detoxification of many poison and drugs (SER)
  • ER is a component of cytoskeleton (spreads as a net) of cell and provides mechanical support and shape to the cell.
  • Camilo golgi (1898) discovered golgi complex in nerve cell of owl. He observed densely stained reticulas structures near nucleus.
  • GC - present in all eukaryotic cells but in plants these are scattered irregularly in cytoplasm and called as dictyosomes.
  • Golgi body is made up of A parts cisternae, tubules, secretory vesicle, golgian vocuoles strictures are called cisternae. The cisternae at the convex end of the dictyosome comprise forming face (F faue) or cis face while the cisternae at the concave end comprises the maturing face (M face) or trans face.
  • The main function of golgi body is secretion, so it is large sized among the secretory cells.
  • Glycosidation of lipids (addition of carbohydrate to produce glycolipids), glycosylation of proteins (addition of carbohydrate to produce glycoproteins), are also the function of glogi complex.
  • It helps in the formation of primary lysosomes.
  • Lysosomes are microscopic, vesicular structure which is bounded by single membrane (lipoproteinous) and involved in intracellular digestive activities containing hydrolytic enzymes. These are popularly called "suicidal bags".
  • On the basis of their contents four types of lysosomes are exist. That are, primary lysosomes, secondary lysosomes, tertiary lysosomes/residual bodies, Autophagosomes / autolysosomes.
  • Functions of lysosomes are followed by (i) lysosomes of sperm provides enzyme for breaking limiting membrane of egg, eg:- hyaluronidase enzyme.
  • Lysosome imitate cell division by digesting repressor molecules and it also engulf the carcinogens.
  • The vacuole in plants was discovered by spallanzani. It is bounded by differentially (or) selectively permeable membrane, the tonoplast.
  • Vacuoles are Non living reservoir, contain water, minerals and anthocyanin pigments. It may be sap vacuoles, contractile vacuole (or) gac vacus
  • Vacuole maintain osmotic relation of cell which is helpful in absorption of water.

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