STRUCTURE OF EUKARYOTIC CELL ( part 2)

  1. Cell Organelles=                    Cell organelles are sub-cellular structures with characteristic morphological forms, distinctive chemical constitutions and definite functions. An eukaryotic cell possess number of cel organelles as discussed below Endomembrane system It consist of membrane bound organelles which function in close coordination with one another, viz., endoplasmic reticulum, Golgi complex, lysosomes and vacuoles. Nuclear envelope is also considered a part of endomembrane system as its lumen is in continuation with the lumen of endoplasmic reticulum. Organelles like plastids, mitochondria, peroxisomes and glyoxysomes are not a part of endomembrane system.                                        Funcation= Packaging and storage of materials.(i) Secretion of different substances like gum, mucilage and hormones of endocrine glands.                (ii) Acrosome formation during spermatogenesis. (iv) Glycosylation of proteins and lipids to form glycoproteins and glycolipids.                              (v) Transformation and recycling of plasma membrane.                 Lysosome  = Lysosomes first reported by Christian de Duve are single membrane bound, small vesicular organelles, containing enzymes. They are also called as suicidal bags owing to the presence of large number of digestive enzymes or acid hydrolases in them. Lysosomes are presen in all animal cells except RBCS. In plant and fungi, vacuoles take over the function of lysosomes ere are four types of form in same cell is referred to as polymorphism lysosomes on the basis of their morphology and function. The existence of more than one morphology..      Funcation =         1.Lysosomes help in digestion of useful substances for cell's use i.e, intracellular digestion. 
  2.  Harmful (unwanted) material like pathogens, toxic material are disposed off by lysosomes. Thus, lysosomes are also called disposal bags' or disposal units Lysosomal enzymes are used by sperm for breaking limiting membrane of egg thus, aid in fertilisation. They are recycling centres of cell and help in renewal of worn out cells and organelles. In the thyroid gland, thyroglobulin is hydrolysed by lysosomal enzymes to form active thyroxine hormone. .                   Vacuoles are non-cytoplasmic areas present inside the cytoplasm. These are surrounded by single membrane called tonoplast. TheyMaintains osmotic pressure andIt contains digestive enzymes which Types of vacuoles =Food vacuole=Sap vacuole=Helps in food digestion. are formed by expansion and pinching off turgidity from endoplasmic reticulum. They are small in Sfores waterslub animal cell and large in fungal and plant cells. Vacuoles may be of four types, depending upon its contents and functions. help in digestion of nutrients vacuolar pigments e.g, anthocyanir Air vacuole e Stores gases It also provides buoyancy, mechanical Contractile vacuole. Regulate osmoregulation and excretion strength and protection from harmful radiations.
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