Form closed compartments to avoid exposing

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Unformatted text preview: the lipid while but the key properFes of polar head group/ nonpolar tail group intact If you know a lipid is a phosphoglyceride, does that say anything about the structure of the faCy acids linked to the glycerol backbone? Review Mix and match faXy acids with different backbones and different polar head groups •  •  •  •  Polar head group ? What is the backbone molecule, glycerol or sphingosine? Where is the faXy acid covalently linked to the backbone ? Are the faXy acids saturated or unsaturated? Lipids form diverse three ­dimensional assemblies •  Micelles are spherical assemblies with the hydrophobic tails sequestered in the interior. Detergents in parFcular form micelles. •  Lipid bilayers can form extended planar assemblies. •  However, bilayers are very flexible and can form closed structures called vesicles with water in the interior. Rules for bilayer self assembly •  Stabilized primarily by hydrophobic interacFons between the nonpolar tails •  Further stabilized by van der Waals interacFons as well as hydrogen bonding between the polar head groups and water. •  Form closed compartments to avoid exposing hydrocarbons to water. •  Any holes that form in the bilayer are energeFcally unfavorable so bilayers are self ­sealing. Permeability of ions and molecules is related to their solubility in nonpolar solvents Polar or charged molecules must be desolvated polar large molecules nonpolar small molecules Where on this scale would you expect to find the following; Molecular oxygen (O2)? Hb? Fluid Mosaic Model exposed to extracellular •  Proteins and lipids are free to move laterally in the plane of the bilayer •  Lipids are a great barrier, but membranes need proteins to perform their biological funcFons Membrane fluidity is affected by temperature Membranes must remain fluid and flexible for membrane proteins to funcFon properly Number of double bonds and length of faXy acyl chains affect membrane fluidity How do you explain this observa5on? Saturated fats have higher melFng temperatures than unsaturated fats Unsaturated How would the length of the hydrocarbon tail affect the melFng temperature? Bacteria regulate membrane fluidity by altering the faXy acid composiFon of their membranes Membrane fluidity ? More unsaturated chains ? More saturated chains ? Constant mobility maintained at differen...
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This test prep was uploaded on 02/25/2014 for the course BIOC 462A taught by Professor Ziegler,baldwin during the Spring '08 term at University of Arizona- Tucson.

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