10-2-09_plasma_membrane3B - Have you seen the roses?...

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Have you seen the roses? There's a whole lot of colours. Syd Barrett What are we at the park for except to win? I'd trip my mother. I'd help her up, brusher her off, tell her I'm sorry. But mother don't make it to third. ~Leo Durocher, former manager of Dodger and Cubs
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Announcements Tests will be available in MJIS 2019 for the next two weeks. Research article summary can be submitted through Blackboard “Bio 230 2009 Research article summary 1” beginning at noon today. Use your own words to describe the paper Article due Monday, October 5, at noon
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Sphingolipids are another membrane lipid All are derivatives of sphingosine (top) Can link to another fatty acid (R) through amino group Sphingosine+Fatty acid= ceramide Different groups can also link to OH at end of ceramide Often, these are sugars, forming glycolipids If simple sugar, cerebroside If complex sugar, ganglioside Ganglioside disorders cause neurological symptoms in humans, such as Niemann- Pick disease
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Membranes are constantly in motion and not static little spherical blobs Scanning electron micrograph of the leading edge of a moving cell However, in order not to expose their hydrophobic cores, there is never a free membrane edge
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Lateral diffusion is by far the main form of movement within membranes Tail movements are fastest Lateral motions are fast, occurring on microsecond scales Phospholipid flipping is quite infrequent (< 1/day) Flipping can be sped up by enzymes (called flippases)
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Cholesterol: your doctor’s favorite lipid No phosphate head Typically polar hydroxyl towards membrane surface Ring structure is rigid and stiffens membrane when present Cholesterol regulation is important not only for heart disease, but also for cell function and signaling Wolfe S.L., Molecular and Cellular Biology, Wadsworth Publishing Company, 1993
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What do motor oil and membranes have in common? Viscosity Viscosity is dependent on the phospholipid organization and movement, which is temperature dependent There is a transition temperature at which lipids go from a liquid phase (left) to a more restricted frozen gel phase (right) Above the transition temperature, liquid (a) with significant tail movement. Below that temperature, crystalline gel phase (b)
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Controlling number of double bonds controls membrane fluidity (viscosity) As number of double bonds increases or fatty acid chain length decrases, transition temperature decreases Can finely control fluidity through membrane composition Fluidity creates opportunities for regulated, dynamic interactions between membrane proteins Fluidity is also critical in the formation and recycling of membranes for exocytosis and endocytosis and protein packaging and insertion
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This note was uploaded on 02/09/2010 for the course BIOL 230 taught by Professor Bartlett,e during the Fall '08 term at Purdue University-West Lafayette.

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10-2-09_plasma_membrane3B - Have you seen the roses?...

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