Exam1_308 - Biochemistry-Pt.I Mid-term exam Block 3, 2008...

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Exam_midterm_Ansrs 1 of 7 B. Nowak-Thompson 11/27/2008 Biochemistry-Pt.I Mid-term exam Block 3, 2008 Name Answer any 10 of the following 13 questions (all are worth 8 pts). Be sure to include molecular details in your answers that support the cause and effect relationships that exist between the chemical mechanisms and physiological results. Part II of this exam is a 20 point case study that is to be handed in no later than 9am tomorrow morning. You may pick this up as you leave the exam today. Please, do not consult with other people on this part of the exam although you may use other resources if you find it necessary. 1. Outline the metabolic relationships among the liver, brain, muscle, and adipose tissue in the fasting state (assume the person is at rest). Be sure to identify the primary fuel source used by each organism and where it is originating. 2. Glucagon and epinephrine elicit similar metabolic responses but differ in the tissue they affect; myocytes lack the glucagon receptor and thus do not respond to this hormone. Rationalize the lack of glucagon receptors with respect to the metabolic relationships between, and functions of, the liver and muscle tissue. Glucagon signals/triggers mobilization of glycogen fuel reserves. Liver glycogen is continuously made and degraded during the course of a day and serves as a glucose reserve used to help maintain homeostasis of blood glucose levels. Muscle glycogen, on the other hand, is a fuel reserve only for the muscles. This glycogen is reserved until physical activity demands large amounts of energy for muscle movement. If muscles responded to glucagon, glycogen would be depleted as a function of diet and may not be on reserve when needed (like when chasing food when you are hungry). Because muscles are the only users of their glycogen stores, it makes sense to have glycogenolysis respond to a “fright or flight” hormone like epinephrine, and not to a fed/fasting signal like glucagon.
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Exam_midterm_Ansrs 2 of 7 B. Nowak-Thompson 11/27/2008 3. Several years ago, the Atkin’s diet gained popularity as a weight loss program. A very crude description of this diet plan is that it advocates reducing carbohydrates and increasing protein consumption in the diet. The figure below illustrates changes in blood chemistry after meals emphasizing either carbohydrates or proteins. How would the Atkin’s approach to weight loss work—in other words, what is the mechanism behind this weight loss strategy? For carbohydrate meal: There is a big change in the relative amounts of glucagon and insulin as a result of glucose consumption. The insulin increase and glucagon decrease signal the body to store glucose as glycogen or process it via glycolysis into acetyl-CoA and then use that to produce fatty acids/TAGs that can be stored in the adipocytes. For the protein meal:
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Exam1_308 - Biochemistry-Pt.I Mid-term exam Block 3, 2008...

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