bio230_ch7ECM_jhpark

bio230_ch7ECM_jhpark - Chapter 7 Interactions Between Cells...

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Chapter 7 Interactions Between Cells and Their Environment Weldon School of Biomedical Engineering Jonghyuck Park
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Cellular trafficking Once a protein is made, where does it go? Most are constructed by ribosomes in the cytosol, and  remain there Others are needed in specific organelles or on the cell  membrane Examples: Hormone receptor proteins Digestive enzymes RNA/DNA polymerases Extracellular matrix components How are these proteins sorted, and afterwards,  how are they delivered?
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Trafficking in the endomembrane system Consists of endoplasmic reticulum  (ER) and Golgi complex Many proteins are synthesized by  ribosomes on the rough ER Proteins and lipids are modified,  packaged, sorted, and transported  by the Golgi complex Proteins and chemicals such as  digestive enzymes are often  packaged in vesicles, which fuse  with the plasma membrane and are  secreted
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Movements of materials within cells are tightly regulated Constitutive secretion:  Always on, unregulated, mainly extracellular  matrix and plasma membrane Regulated secretion:  Materials are synthesized and stored in  membrane bound packages until stimulated to transport to target (e.g.  hormones and neurotransmitters) Proteins, lipids, and carbohydrates all participate in secretory pathways
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Hey bud, let’s party!  Schematic of a secretory pathway Left: Biosynthetic/secretory pathway Right: Endocytic pathway: taking in  substances from outside.  Secretory pathway is: Nucleus to rough  ER (RER) to cis Golgi network to trans  Golgi to trans Golgi network to vesicle to  fusion with target membrane Packaging and targeting is achieved  through protein and/or carbohydrates that  can be used to sort molecules or vesicles
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Endoplasmic reticulum (ER) The ER is an extensive membrane network that encapsulates a large  cisternal space within the cell. ER consists of rough ER (left), which is studded with ribosomes that  produce protein, and smooth ER (right), which does not have  ribsomes on it. 
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Smooth ER (SER) and its functions Rough ER and smooth ER membranes are continuous with each other Extensive in skeletal muscle, kidney tubules, liver In muscle, involved as a major source of intracellular calcium for muscle  contraction or secretion of vesicles In liver, involved in detoxification of ethanol
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Protein doctoring in the rough ER Many proteins are synthesized by ribosomes on ER surface Proteins secreted from cells Soluble proteins that reside within compartments of endomembrane  system (ER, Golgi complex, lysosomes, endosomes, vesicles, plant  vacuoles)
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bio230_ch7ECM_jhpark - Chapter 7 Interactions Between Cells...

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