7BB lecture 10-7-09 mem. transport, potential

7BB lecture 10-7-09 mem. transport, potential - Chapter 7...

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Chapter 7 (pp. 138-139) – Cell membrane functions (conclude) Learning objectives: Explain how bulk transport through the cell membrane is accomplished Chapter 11 (pp.206-225): Cell communication Explain the three stages of cell signaling: Know the difference between: - membrane receptors and intracellular receptors. - a ligand, a messenger molecule, a “2 nd ” messenger - protein kinases and protein phosphatases Explain how signal from a single ligand can be amplified Explain how a specific ligand can affect more than one cell type. Terms to know include…ligand, paracrine signaling, relay molecule, G protein-coupled receptor, receptor tyrosine kinase, ion channel receptor, phosphorylation cascade, kinase, phosphatase, adenylyl cyclase, IP3, DAG, scaffolding protein, dimerization,…. .
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Bulk transport of large proteins across the plasma membrane Occurs by exocytosis and endocytosis Small molecules and water enter or leave the cell through the lipid bilayer or by transport proteins Large molecules, such as polysaccharides and proteins, cross the membrane via vesicles
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Exocytosis In exocytosis Transport vesicles migrate to the plasma membrane, fuse with it, and release their contents Many secretory cells use exocytosis to export their products Example: exocytosis by neuron to release neurotransmitter
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Endocytosis In endocytosis The cell takes in macromolecules by forming new vesicles from the plasma membrane There are three types of endocytosis…
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EXTRACELLULAR FLUID Pseudopodium CYTOPLASM “Food” or other particle Food vacuole 1 µm Pseudopodium of amoeba Bacterium Food vacuole An amoeba engulfing a bacterium via phagocytosis (TEM). 2. PINOCYTOSIS Pinocytosis vesicles forming (arrows) in a cell lining a small blood vessel (TEM). 0.5 µm 2. In pinocytosis , the cell “gulps” droplets of extracellular fluid into tiny vesicles. It is not the fluid itself that is needed by the cell, but the molecules dissolved in the droplet. Because any and all included solutes are taken into the cell, pinocytosis is nonspecific in the substances it transports. Plasma membrane Vesicle 1. In phagocytosis, a cell engulfs a particle by wrapping pseudopodia around it and packaging it within a membrane- enclosed sac large enough to be classified as a vacuole. The particle is digested after the vacuole fuses with a lysosome containing hydrolytic enzymes. Three types of endocytosis Figure 7.20 1. PHAGOCYTOSIS
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0.25 µm 3. RECEPTOR-MEDIATED ENDOCYTOSIS Recepto r Ligand Coat protein Coated pit Coated vesicle A coated pit and a coated vesicle formed during receptor- mediated endocytosis (TEMs). Plasma
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7BB lecture 10-7-09 mem. transport, potential - Chapter 7...

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