320Fall09Midterm3Prep_key - Cell Biology(BIO 320 Fall 2009...

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Cell Biology (BIO 320), Fall 2009, Dr. Bushart Supplemental Homework for Midterm #3 General topic list ( Lectures 12-18): Transport into ER Coated vesicles Vesicle targeting and fusion ER to Golgi Golgi Lysosomes Endocytosis Exocytosis Cytoskeletal subunits Actin and actin filaments Tubulin and microtubules Nucleation Severing Binding proteins Practice activities : 1. Review homework questions. a. Homework #5: 1, 2, 5. 6, 7 b. Homework #6: 1, 2, 3, 5 c. Homework #7: 1, 2, 3, 5 Old questions 1. What role do H + -ATPases play in the delivery of acid hydrolases to endosomes? Why are the acid hydrolases not active in the endosome? H + -ATPases acidify the endosomes. This pH difference allows the M6P receptors to unload their cargo (the acid hydrolases). While, acid hydrolases require low pH to function, they also need an additional modification, such as the removal of an inhibiting peptide region. This ensures that the hydrolases will not be active even in the low pH environment of the lysosome. 2. A random molecule (X) gets taken up passively into a coated vesicle along with a cargo molecule (Y) during a receptor-mediated endocytosis event. The receptors in this vesicle are destined to return to the plasma membrane. Give answers and explanations to the following questions (4 pts each): a. Where will the receptors’ cargo (molecule Y) likely end up? b.
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This note was uploaded on 01/25/2010 for the course BIO 51055 taught by Professor Bushart during the Fall '09 term at University of Texas.

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320Fall09Midterm3Prep_key - Cell Biology(BIO 320 Fall 2009...

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