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Cell Organelles. Prof. Dr. Mohammad Ahmed Azmi, Ph.D. Membranous Organelles Endoplasmic Reticulum (ER) Network of tubular and vesicular structures which are interconnected with each other It is covered by limiting membrane composed of protein & lipid bi-layer
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Cell Organelles Prof. Dr. Mohammad Ahmed Azmi, Ph.D.
Membranous Organelles • Endoplasmic Reticulum (ER) • Network of tubular and vesicular structures which are interconnected with each other • It is covered by limiting membrane composed of protein & lipid bi-layer • Lumen of ER contains a fluid called endoplasmic matrix • ER forms a link between nucleus and cell membrane • OR • Forms connection of cell membrane with the nuclear membrane • Granular or Rough A granular or Smooth ER
Granular or Rough ER A granular or Smooth ER • Ribosomes are attached on the surface of ER • Synthesis of proteins • Role in the degradation of worn out cytoplasmic organelles like mitochondria • Donot have ribosomes • Synthesize lipids, steroid hormones • Also involved in the detoxification of some drugs
Mitochondria • rod-shaped or oval shaped • Covered by lipid bi-layer membrane • Outer membrane is irregular & folded forming shelves – cristae • Inner space of cristae – called mitochondrial matrix • Matrix contains many enzymes and protein molecules for involved in respiration & formation of ATP • Power house of cell
Golgi Apparatus • Consists of 5 to 8 membranous sacs usually flattened in structure called cisternae • Situated near the nucleus • Present in all cells but larger in those that synthesize & export proteins. • Proteins move from rough ER to the gogli apparatus where they are packaged into secretory vesicles called secretory granules • The seceretory vesicles are stored & when proteins are needed they move to the cell membrane & so proteins are exported.
Lysosomes • They are oval or spherical membrane bound vesicular organelle • Found throughout the cytoplasm • Enzymes formed in rough ER are processed and packed in the form of small vesicles in the golgi apparatus • These vesicles are then moved out from golgi apparatus and become the lysosomes. • Lysosomes Primary lysosomes Inactive in nature containing Hydrolytic enzyme Formed from Golgi apparatus Secondary lysosomes Active containing lysosomal enzymes proteases, lipases amylases nucleases
Peroxisomes • Are microvesicular structures like lysosomes. • They are pinched off from ER & not from golgi apparatus. • Contain some oxidative enzymes in the phagocytosis of foreign particles
Centrosome and Centrioles • Membranous bound cellular organelle, cylindrical in shape • Situated in the centre of cell and close to nucleus • Responsible for the movement of chromosomes during cell division.
Non-membranous Organelles • Ribosomes • Non-limiting cellular organelle • Granular and small dot-like structure • Made up of proteins (35%) and RNA (65%) • RNA present in ribosomes are called r-RNA • Ribosomes are responsible for protein synthesis Attached to ER Free ribosome in the cytoplasm Responsible for protein of Hb, peroxisome & mitochondria Protein formation
Cytoskeleton: Consists of: • -Microtubules • -Microfilaments • Cell organelles that determine the shape of cell & support • Also responsible for cellular movement and response of cell to external stimuli • Microtubuls • Spindle fibers • Cilia • Flagella • Actin & myosin
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