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bio 320 exam 2 answer key

bio 320 exam 2 answer key - BIO 320 Dr Bushart Midterm...

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BIO 320 Dr. Bushart Print Name:___________________________ Midterm Exam #2 10 AM Tuesday August 5, 2008 General instructions : Read each question carefully and don’t hesitate to ask if a question seems unclear. Trying to provide an answer for every question is advantageous; you will not be penalized for guesses. The short-answer questions have specific answers, although for some, more than one answer is possible. If possible, answer each question in the space provided, but if needed, continue on the back. If you use a drawing as part of your answer, be sure to also include appropriate labeling and/or a short written explanation. To receive full credit you must clearly and fully answer the question being asked. Partial credit may be given in 0.5 point increments. This exam is worth 100 points (the points for each section/question are noted in parentheses). Short answer (100 points): There are 9 short-answer questions. Write a clear concise answer for each question. Some questions may have more than one possible answer but require you to defend your choice. Be sure you include clear explanations. Make sure your response answers the question being asked! 1. (10 points) Mitochondrial import is a post-translational process; a polypeptide is first fully synthesized in the cytosol by free ribosomes. Consider the formation of a multi-subunit mitochondrial matrix protein . a. Would you expect a mitochondrial signal sequence on only one subunit to be sufficient for correct localization or would each polypeptide need to have its own? Explain. Each polypeptide would need its own signal sequence. Mitochondrial proteins are imported as unfolded polypeptides so [unlike nuclear import] a signal on one subunit is not sufficient to result in the import of all the subunits. Each one must be imported one at a time. b. As mentioned in class, the TIM and TOM translocators do not specifically require each other for transport functionality. However, one of these transporters is required for specificity. Which translocator satisfies this requirement and why? The TOM complex is required for specificity because it is the transporter associated with the receptors for import. No receptors, no recognition, no specificity.
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2. (12 points) The following diagram is of a multipass transmembrane protein found in the ER. Hexagons ( ) indicate N-linked oligosaccharide modifications. a. If the hexagons represent high-mannose oligosaccharides, is this protein likely to be in the ER or the Golgi? Why? This protein would have arrived in the Golgi. While N-linked oligosaccharides are added in the ER, they are only modified into the high-mannose type in the Golgi.
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