3574008077001

3574008077001 - TA: Jason Smith Email: Jes008@ucsd.edu OH:...

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TA: Jason Smith OH: Weds 4-5pm Sun God Lounge BICD 110 Email: Jes008@ucsd.edu LECTURE 4 Cell membrane : thin layer of dynamic and fluid lipid and protein molecules held together by interactions **HOW THICK?**: LIPID BILAYERS Closed lipid bilayer membranes are energetically favorable Due to the fact that membrane lipids are :both hydrophilic and hydrophobic Closed bilayer ordering of water, which increases entropy! o Increasing entropy (ΔG= ) is good! Properties of lipid bilayer : Phospholipids can diffuse laterally easily Phospholipids can’t - easily! o Need special enzymes to do this o This property gives rise to the very important distributions of phospholipids on different sides of the membrane Saturation of tails o Increase membrane becomes fluid o Decrease membrane becomes fluid Four major phospholipids found in mammalian PM’s: 1) 2) 3) 4) -Sphingolipid vs phosphoglyceride Cholesterol - Acts to fill in the gaps between phospholipids and prevent leakage - fluidity at lower temps prevents freezing/gel formation Problem: A fish that lived in Antarctica would want more phospholipids and Levels of cholesterol in its cell membranes Why? Lipid Rafts – small areas of membrane where and are concentrated Many of the proteins are o Makes the raft areas slightly thicker can be indirectly seen with atomic force microscopy o Never seen through a microscope, still debated as to whether they actually exist Asymmetric Distribution (how is this accomplished?) OUTSIDE: Phosphatidyl choline
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Sphingomyelin Glycolipids INSIDE: Phosphatidyl ethanolamine
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3574008077001 - TA: Jason Smith Email: Jes008@ucsd.edu OH:...

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