Membranes - the inside of the bilayer (see the diagram...

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Membranes Plasma Membrane The plasma membrane surrounds the cell and functions as an interface between the living interior of the cell and the nonliving exterior. All cells have one. It regulates the movement of molecules into and out of the cell. Membrane Structure The fluid-mosaic model states that membranes are phospholipid bilayers with protein molecules embedded in the bilayer. Phospholipids Most of the lipids in a membrane are phospholipids . Phospholipids contain glycerol, two fatty acids, and a phosphate group. The phosphate group is polar ( hydrophilic ), enabling it to interact with water. The fatty acid tails are nonpolar ( hydrophobic ) and do not interact with water. Phospholipid Bilayers Phospholipids spontaneously form a bilayer in a watery environment. They arrange themselves so that the polar heads are oriented toward the water and the fatty acid tails are oriented toward
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Unformatted text preview: the inside of the bilayer (see the diagram below). In general, nonpolar molecules do not interact with polar molecules. This can be seen when oil (nonpolar) is mixed with water (polar). Polar molecules interact with other polar molecules and ions. For example table salt (ionic) dissolves in water (polar). The bilayer arrangement shown below enables the nonpolar fatty acid tails to remain together, avoiding the water. The polar phosphate groups are oriented toward the water. . Exocytosis Exocytosis moves material to the outside. A vesicle fuses with the plasma membrane and discharges its contents outside. This allows cells to secrete molecules. The fusion of vesicles to the plasma membrane adds membrane to the cell surface....
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Membranes - the inside of the bilayer (see the diagram...

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