Exam2Key2008 - Name: _ Net ID: _ Section: _ EXAM II Key...

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Name: _______________________ Net ID: ___________________ Section: ____ Page 1 EXAM II Key March 12, 2008 BIOCHEMISTRY 462B - SPRING 2007 Write your name and UA Net ID on ALL pages ! There are 9 questions and 100 POINTS total in this exam. This Exam has 7 pages (including this face page). Read all questions carefully. Show your work on mathematical problems, including units. Answer briefly in the space provided. Explain all answers. (Filling all available space is NOT necessary for full credit!).
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Name: _______________________ Net ID: ___________________ Section: ____ Page 2 1. (10 points) Please compare the differences between lipoprotein lipase and hormone- sensitive lipase with regard to substrates and the cell types they are associated with. Answer. Lipoprotein lipase catalyzes breakdown of triglycerides within lipoprotein particles such as chylomicron. It is located in the extracellular matrix of endothelial cells facing blood. Hormone-sensitive lipase catalyzes breakdown of triglyceries within adipocytes. 2. (10 points) In Problem Set 5, you learned how to measure fatty acid oxidation using [1- 14 C]oleic acid. It is also possible to measure fatty acid oxidation by following production of 3 H 2 O from [ 3 H]oleic acid. The tritiated label is transferred to water during oxidation of reduced electron carriers. Please identify the electron carriers that transfer electrons as part of hydride ions ( 3 H ) and hydrogen atoms ( 3 H) from oleic acid and the pathways during which electrons are transferred to O 2 . Answer. The tritium label from oleic acid is transferred to NAD + and FAD as hydride ions or hydrogen atoms during β -oxidation and citric acid cycle (full credit given if TCA cycle is omitted and β -oxidation/oxidative phosphorylation are discussed). From there the tritium label is transferred to O 2 through electron transport chain during oxidative phosphorylation. 3. (14 points) In TCA cycle, α -ketoglutarate dehydrogenase complex catalyzes the following reaction: (A) One potential effect of inhibiting α -ketoglutarate dehydrogenase complex is decreased utilization of ketone bodies and their subsequent accumulation in muscle . Please explain why this occurs. (B) Another potential effect of such inhibition is increased ketone body production in liver . Please explain why this occurs. Answer. (A) Blocking citric acid cycle would cause buildup of acetyl-CoA, which may cause feedback inhibition of ketone body utilization and depletion of coenzyme A. In addition, succinyl-CoA is needed to transfer a CoA to acetoacetate during conversion of ketone bodies to acetyl-CoAs. Either answer will be given full credit. (B) Inhibition of citric acid cycle in liver would lead to increased flux toward
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Exam2Key2008 - Name: _ Net ID: _ Section: _ EXAM II Key...

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