D103 TA midterm review

D103 TA midterm review - W2009 Bio D103: TA MIDTERM EXAM...

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W2009 Bio D103: TA MIDTERM EXAM REVIEW Wednesday, Feb. 4, 4-6pm DBH 1100 Liz McReynolds (Lectures #2-4) Darius Gleason (Lectures #5-9) Helen Fong (Lectures #10-13) Lecture 2: Biological membranes I: Biomembrane structure 1. Membranes Terms and concepts a. Fluid mosaic model of biological membranes Lipids assemble into bilayers in which proteins form the active components of signal transduction and transport 1) Fluidity of the membranes is critical for their function some functions are listed below. 1. Fusion of membranes with each other a. Vesicles with organelles or membrane 2. Diffusion of new lipids and new proteins laterally a. Equal distribution 3. Diffusion of proteins and other molecules laterally across the membrane a. Important in cellular signaling and enzymatic reactions 4. Proper separation of membranes during cell division b. What makes up a membrane? 1. Phospholipids Phosphate-head group (polar) Two long chain fatty acids (non polar) Phospholipids aggregate to hide their hydrophobic tail inside and expose hydrophilic head to the outside There are 4 major types of membrane phospholipids [Type text]
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o PC, SM found outer (exoplasmic) leaflet o PE, PS found inner (cytosolic) leaflet Sphingomyelin (SM): Phosphatidylserine (PS): usually kept on the inner- leaflet, the cytosolic side, of cell membranes by an enzyme called translocase. Phosphatidylcholines (PC): incorporates choline as a headgroup Phosphatidylethanolamine (PE) 2. Cholesterol: Plate like steroid rings interact with and partially immobilize neighbor hydrocarbon chains; has a lipid ordering effect (for most lipids) so lipids are less fluid Cholesterol makes the bilayer less deformable in this region, thereby decreasing the permeability of membrane to small water-soluble molecules Considered a membrane lipid (amphipathic) Abundant in animal lipid bilayers Found in both leaflets Makes membrane able to pack phospholipids in a more tightly packed configuration Important in formation of lipid rafts c) Requirements for a biological membrane Permeability barrier that separates inside from outside Flexible (fluid ) so that a cell can respond to its environment Selectively permeable to allow molecule exchange with the environment The structure of a lipid determines its packaging in an aqueous environment [Type text]
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1. Cell membrane types External(plasma) membrane = cell membrane Internal membranes = organelle membranes 2. Lipid rafts A cholesterol-enriched micro-domain in cell membranes Lipid rafts are resistant to non-ionic detergents (“mild” detergents such as Triton X-100) When such a detergent is added to cells, the fluid membrane will dissolve while the lipid rafts may remain intact and can be extracted d) What regulates membrane fluidity? 1.
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This note was uploaded on 02/21/2009 for the course BIOL 05400 taught by Professor Taagepera,s during the Spring '09 term at UC Irvine.

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D103 TA midterm review - W2009 Bio D103: TA MIDTERM EXAM...

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