MEMBRANE STUCTURE AND FUNCTION - fluid mosaic model • A...

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MEMBRANE STUCTURE AND FUNCTION Introduction The plasma membrane separates the living cell from its nonliving surroundings. This thin barrier, 8 nm thick, controls traffic into and out of the cell. Like other membranes, the plasma membrane is selectively permeable , allowing some substances to cross more easily than others. A. Membrane Structure The main macromolecules in membranes are lipids and proteins, but include some carbohydrates. The most abundant lipids are phospholipids. Phospholipids and most other membrane constituents are amphipathic molecules . Amphipathic molecules have both hydrophobic regions and hydrophilic regions. The phospholipids and proteins in membranes create a unique physical environment, described by the
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Unformatted text preview: fluid mosaic model . • A membrane is a fluid structure with proteins embedded or attached to a double layer of phospholipids. 1. Membrane models have evolved to fit new data • Models of membranes were developed long before membranes were first seen with electron microscopes in the 1950s. • In 1895, Charles Overton hypothesized that membranes are made of lipids because substances that dissolve in lipids enter cells faster than those that are insoluble. • Twenty years later, chemical analysis confirmed that membranes isolated from red blood cells are composed of lipids and proteins. • Attempts to build artificial membranes provided insight into the structure of real membranes....
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MEMBRANE STUCTURE AND FUNCTION - fluid mosaic model • A...

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