Exam2Key2007 - Name: _ Net ID: _ Section: _ EXAM II Key...

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Name: _______________________ Net ID: ___________________ Section: ____ Page 1 EXAM II Key March 7, 2007 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 8 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. (12 points) (a) Name three major constituents of a chylomicron. Answer. Major constituents of chylomicrons include triacylglycerol, cholesterol, cholesteryl esters, apolipoproteins (B-48, C-II, C-III, E). (b) Chylomicrons can be separated from other lipoproteins (chylomicron remnants, HDL, LDL, etc) and measured using either traditional density gradient ultracentrifugation or more recently, proton NMR. What is the expected level of circulating chylomicrons (higher, lower, or the same as the average) following a regular meal in an individual with inherited defect in lipoprotein lipase and why? Lipoprotein lipase deficiency strikes one in one million births, often with devastating effects. Answer. This individual should have higher than average levels of chylomicron since the triacylglycerol in chylomicron cannot be broken down by lipoprotein lipase. (c) As a reproductive endocrinologist, a couple was referred to you because they have not been able to produce a child. After some tests, you find the man is not producing any functional sperm. Not able to identify a cause, you search the research literature and find a paper describing the importance of lipid metabolism in spermatogenesis. Looking over the man’s medical records, you see that there were very low levels of fatty acids and glycerol in his blood following a 12-hour fast. But levels of fatty acids and glycerol are normal immediately after a meal. What enzyme do you think is missing in this individual? If you forgot the proper name of the enzyme, describe the general class of enzyme it belongs to and which tissue site it is present. Answer. (c) Hormone-sensitive lipase. 2. (6 points) Cattle and other ruminant animals produce propionate as a result of cellulose fermentation by microorganisms in rumen. In many parts of the world (Australia, for example), cattle cannot obtain sufficient cobalt from the grass and suffer from stunted growth as a result. Given the fact that cobalt deficiency affects lactating cows more so than other types of cattle, please provide a plausible explanation for this condition by describing the reaction (by enzyme name or substrate and product) that requires cobalt and the reason why this condition affects lactating cows disproportionately. Answer.
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This note was uploaded on 04/07/2009 for the course BIOC 462b taught by Professor Grimes,tsao,borque during the Spring '08 term at University of Arizona- Tucson.

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Exam2Key2007 - Name: _ Net ID: _ Section: _ EXAM II Key...

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