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11:06 AM 55% LD iPad learn uco.edu Kara Ek... o ...al I sguy I. Dynamics 12th Statics 6th Editi... Biology questio XO Bio2203 Hw... My Home Cell Biology h A My Media ePortfolio D2L Help Learn UCO Cell Biology 30700.201530 UNIVERSITY OF CENTRAL OKLAHOMA COURSE HOME CONTENT RESOURCES V COMMUNICATION v ASSESSMENTS V Table of Contents 1. Intro and Membranes Bio2203 HW1 S15 W Bio 2203 HW1 S 15 4. Explain membrane fluidity and what contributes to it. View as Text OB Send to Binder Reflect in ePortfolio Download Activity Details You have viewed this topic Last Visited Jun 3, 2015 10:07 AMExplanation / Answer
, membrane fluidity refers to the viscosity of the lipid bilayer of a cell membrane or a synthetic lipid membrane. Lipid packing can influence the fluidity of the membrane. Viscosity of the membrane can affect the rotation and diffusion of proteins and other bio-molecules within the membrane, thereby affecting the functions of these molecules.
Membrane fluidity can be affected by a number of factors.One way to increase membrane fluidity is to heat up the membrane. Lipids acquire thermal energy when they are heated up; energetic lipids move around more, arranging and rearranging randomly, making the membrane more fluid. At low temperatures, the lipids are laterally ordered and organized in the membrane, and the lipid chains are mostly in the all-trans configuration and pack well together. The composition of a membrane can also affect its fluidity. The membrane phospholipids incorporate fatty acids of varying length and saturation.
Lipids with shorter chains are less stiff and less viscous because they are more susceptible to changes in kinetic energy due to their smaller molecular size and they have less surface area to undergo stabilizing van der Waals interactions with neighboring hydrophobic chains. Lipid chains with double bonds are more fluid than lipids that are saturated with hydrogen and thus have only single bonds. On the molecular level, unsaturated double bonds make it harder for the lipids to pack together by putting kinks into the otherwise straightened hydrocarbon chain. Membranes made with such lipids have lower melting points: less thermal energy is required to achieve the same level of fluidity as membranes made with lipids with saturated chains. Incorporation of particular lipids, such assphingomyelin, into synthetic lipid membranes is known to stiffen a membrane. Such membranes can be described as "a glass state, i.e., rigid but without crystalline order".Cholesterol acts as a bidirectional regulator of membrane fluidity because at high temperatures, it stabilizes the membrane and raises its melting point, whereas at low temperatures it intercalates between the phospholipids and prevents them from clustering together and stiffening. Some drugs, e.g. Losartan, are also known to alter membrane viscosity. Another way to change membrane fluidity is to change the pressure.[1] In the laboratory, supported lipid bilayers and monolayers can be made artificially. In such cases, one can still speak of membrane fluidity.
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