Cell Membranes Semi-permeable Lipid bilayer. Function of Plasma Membrane Physically separates cell...
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![Page 1: Cell Membranes Semi-permeable Lipid bilayer. Function of Plasma Membrane Physically separates cell from outside world Maintains homeostasis Regulates.](https://reader030.fdocuments.us/reader030/viewer/2022032806/56649f0b5503460f94c1e88a/html5/thumbnails/1.jpg)
Cell Membranes
Semi-permeable
Lipid bilayer
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Function of Plasma Membrane Physically separates cell from outside world
Maintains homeostasis
Regulates passage of materials into and out of cell
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Endomembrane System Membranes of organelles such as:
Nuclear membrane Endoplasmic Reticulum Golgi Complex Vesicles/Vacuoles Lysosome
Divide cell into compartments
Serve as surfaces for chemical reactions
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Basic Structure of the Membrane
Made of phospholipids:
Hydrophilic head Glycerol + PO4
Hydrophobic tail 2 fatty acid chains
Since cells are in an aqueous solution, bilayer is most stable form
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Additional Molecules
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Fluid Mosaic Model Currently accepted molecule of plasma
membrane structure
Lipids of membrane are fluid and move laterally
Proteins are embedded/scattered throughout
http://home.earthlink.net/~shalpine/anim/Life/memb.htm
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Membrane Proteins Arranged asymmetrically
2 main types:
Integral proteins May be transmembrane
Peripheral proteins
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Functions of Membrane Proteins: Passive transport - passageways
Active transport – pump materials
Enzymes – catalyze reactions
Signal Transduction
Identification
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Membrane Potential Cell membrane is polarized
Inside of cell is more neg. than outside Electrical gradient
Voltage Can be used to do work
Membrane potential = voltage Resting potential = -70mV
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Cell Junctions Form between cells in
close contact with one another
Allow for rapid communication, prevent passage of material, form strong connections
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Cell Junctions: Tight junctions
Gap junctions
Anchoring Junctions Desmosomes Adhering Junctions
Plasmodesmata