9-19 - Membrane Fluidity Membrane fluidity refers to the...

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Membrane Fluidity The lipids may exist in either state and the temperature at which they pass from one state to the other is known as the transition temperature . Membrane fluidity refers to the physical state of the lipids in the bilayer. The lipids can exist in two states: 1. a two-dimensional liquid crystal in which the lipids are able to move within plane of one leaflet of the bilayer; 2. a frozen crystalline gel in which the movement of the lipids is greatly restricted.
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Two-dimensional liquid crystal Crystalline gel
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The transition temperature of a lipid bilayer depends on the particular lipids of which it is constructed. 1.The degree of unsaturation of the fatty acids 2. The length of the fatty acid chains
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3. The presence of cholesterol Cholesterol molecules disrupt the close packing of fatty acyl chains and interfere with their mobility. The presence of cholesterol tends to abolish sharp transition temperature and creates a intermediate fluidity. Temperature Crystalline gel Liquid crystal
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The Biological Significance of Membrane Fluidity 1. The two-dimensional liquid crystal is compromise between a rigid, ordered structure that would lacks mobility and a completely fluid, nonviscous liquid in which the components of the membrane could not be oriented and structural organization and mechanical support would be lacking. 2. The fluidity allows for interactions to take place within the membrane. 3. Fluidity is essential to membrane assembly. The growth of membrane is accomplished by the insertion of lipid and protein components into the fluid matrix of the membranous sheet. 4. Many of the most basic cellular processes, including cell movement, cell growth, cell division, and secretion etc. depend on the movement of membrane components.
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Maintenance of Membrane Fluidity To keep the membrane in a fluid state, cells respond to changing conditions by altering the types of phospholipids of the membrane. Cold response:
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9-19 - Membrane Fluidity Membrane fluidity refers to the...

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