Membranes - Biology 111, Principles of Biology Lecture...

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Biology 111, Principles of Biology Lecture Outlines Biological membranes are selectively permeable boundaries that surround all cells. Phospholipids are a major constituent of all biological membranes (see Figure 5.13): Recall the behavior of phospholipids when mixed with water (see Figure 7.2): Spontaneously form a phospholipid bilayer These bilayers may form a continuous sphere that essentially creates a "bag", in which the interior is separated from the external environment by the phospholipid bilayer. The formation of such a compartment was an important step in the development of the first primitive cell. A phospholipid bilayer creates a SELECTIVELY PERMEABLE barrier to movement of molecules between the inside and the outside environment. Only certain types of molecules can pass through the hydrophobic environment formed by the fatty acid tails of the phospholipid bilayer: small nonpolar molecules water gasses (CO 2 , O 2 ) Molecules that cannot pass through a phospholipid bilayer: polar or charged molecules (ions) large bulky molecules (hydrophilic or hydrophobic) The phospholipid bilayer is not rigid (see Figure 7.5): Phospholipids are continuously moving laterally within a given phospholipid monolayer Unsaturated fatty acid tails contribute to the fluidity of the membrane
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This note was uploaded on 04/17/2008 for the course BIOL 111 taught by Professor Lux during the Fall '07 term at Lander.

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Membranes - Biology 111, Principles of Biology Lecture...

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