320Fall2010Midterm1_Key - BIO 320 Dr. Bushart Midterm Exam...

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BIO 320 Dr. Bushart Print Name:___________________________ Midterm Exam #1 Class (circle one): Tuesday September 14, 2010 MWF 9am MWF 10am TTh 2pm 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 diagram 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). Use pen if you want a chance for a regrade. Short answer (100 points): There are 12 short-answer questions over 4 pages. 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. (8 points) When considering membranes under cold temperatures, BIO 311C students often assume that a thick lipid bilayer is better for a cold environment (they feel it will have greater insulation capacity). Explain how thick membranes are actually worse than thinner membranes in cold environments. Your answer should address the properties of lipids found in such a bilayer. Membrane thickness is determined by 2 factors of the phospholipids: saturation and tail length. Thick membranes have higher levels of saturation and longer tails. Either of these factors slows down the fluidity of a membrane (through tighter packing or greater van der Waals opportunities). This is a problem for cold membranes because the membrane will freeze/gel/crystallize easier (so at a higher temperature) and frozen membranes are bad for cell survival. 2. (8 points) If the net quantity of a protein in a living cell doesn’t change but its activity decreases, what are two features or processes might you look for to determine why its activity has decreased? Explain your choices. Protein activity can be controlled by: Phosphorylation. This can be either removal or addition of a phosphate, which can change the shape of the protein or even modify its interactions with other cell components. (Neither addition nor removal is specifically favored since it depends on each specific protein as to what the phosphate will do).
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This note was uploaded on 09/21/2010 for the course BIO 320 taught by Professor Staff during the Fall '08 term at University of Texas at Austin.

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320Fall2010Midterm1_Key - BIO 320 Dr. Bushart Midterm Exam...

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