Cbio Exam 2

Cbio Exam 2 - 1 BIOL/CBIO 3400 Spring 2011 Second Quiz...

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1 BIOL/CBIO 3400 NAME: Spring 2011 Second Quiz Starai/Fechheimer QUESTION 1 ( 25 POINTS ) (a) (15 POINTS) Describe the primary steps involved in the process of vesicular transport. Begin with a vesicle that has just budded off from a donor membrane, and end when this vesicle has fused with its target. For each step, describe the molecules that participate, their functions, and interactions. Uncoating : Clathrin coat is removed by Hsp70, an ATPase; COPII coat is removed by hydrolysis of Sar1-GTP; COPI coat is removed by hydrolysis of Arf1-GTP. Transport : Rab effectors facilitate association of vesicle with motor proteins such as myosin, dynein, or kinesin, which travel along protein filaments made of actin or microtubules. Tethering : Rab-GDP is cytosolic, but can be activated by a Rab-GEF which exchanges GDP for GTP. Rab-GTP associates with vesicle membranes and can interact with Rab effectors on the target membrane, tethering the vesicle. Docking : As the vesicle gets closer, v-SNAREs on the vesicle can interact with t-SNAREs on the target. Their interaction forms a coiled coil complex. Fusion : the transition from a trans SNARE complex to a cis SNARE complex is like a zipper, bringing the vesicle in apposition with the target membrane, mediating fusion. (b) (10 POINTS) i. Explain the distribution of phosphatidyl choline and phosphatidyl serine in the plasma membrane of a vertebrate cell. PC = extracellular/outer leaflet of PM PS = cytosolic/inner leaflet of PM ii. Trace the distribution and topology of these two phospholipids from their site of synthesis to the plasma membrane, and point out any specific mechanisms that are required to attain the final distribution described in part i. PC: -made on cytoplasmic (outer) leaflet of ER -flipped to luminal (inner) leaflet by ER PC translocase -vesicle transport via Golgi - stays on luminal leaflet -fusion to PM causes it to be on extracellular leaflet PS: -made on cytoplasmic leaflet of ER -vesicle transport via Golgi - stays on cytosolic leaflet -fusion to PM causes it to be on inner leaflet -amino phospholipid translocase will flip any PS on extracellular leaflet of PM back to cytoplasmic leaflet **Note: cytoplasmic ER leaflet becomes cytoplasmic PM leaflet; (outer becomes inner) lumenal ER leaflet becomes EXTRACELLULAR PM leaflet (inner becomes outer)
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This note was uploaded on 04/16/2011 for the course CBIO 3400 taught by Professor Shen,kipreos during the Spring '08 term at UGA.

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Cbio Exam 2 - 1 BIOL/CBIO 3400 Spring 2011 Second Quiz...

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