cytoplasmic_membrane

cytoplasmic_membrane - Cytoplasmic Membrane Systems:...

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Cytoplasmic Membrane Systems: Structure, Function, And Membrane Trafficking An Overview of the Endomembrane System and Its Dynamic Nature I. Before the 20th century - stained tissue sections hinted at an extensive membrane network in cytoplasm A. 1940s - EM revealed diverse array of membranous structures in cytoplasm of most eukaryotes 1. Membrane-bound vesicles of varying diameter; containing material of different electron density 2. Long channels bounded by membranes that radiate through cytoplasm; form an interconnected network of canals 3. Stacks of flattened, membrane-bound sacs ( cisternae ) was subdivided into a variety of distinct membrane-bound compartments D. Current evidence suggests that peroxisomes have a dual origin II. These organelles are part of dynamic, integrated network; materials are shuttled between parts of cell A. Transport vesicles shuttle things between organelles; form by budding from donor compartment B. Transport vesicles move in directed manner, often pulled by motor proteins operating C. When they reach their destination, they fuse with acceptor compartment, which along numerous pathways traversing the cell III. Several distinct pathways through cytoplasm have been identified; they fall into IV. Biosynthetic (secretory) pathway – synthesis in ER (protein) or Golgi (lipid, carbohydrate); altered as pass through Golgi, sent from there to various locations (membrane, lysosome, large plant cell vacuole, etc. secretion from cell itself
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2. Regulated - secretory materials are often stored in large, densely packed, membrane- bound secretory granules in cell periphery; secreted after correct stimulus a. Endocrine cells release hormones b. Pancreatic acinar cells release digestive enzymes c. Nerve cells release neurotransmitters biosynthetic or secretory pathway; discussion will center on several distinct classes of proteins V. Endocytic pathway - moves materials or membrane surface into cell from outside to cytoplasmic compartments (endosomes, lysosomes); movement direction is opposite to that of secretory pathway receptors in transport vesicle walls that recognize them (analogous to trucks carrying different
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cytoplasmic_membrane - Cytoplasmic Membrane Systems:...

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