C485 Exam II Fall ‘13
Name___________________
Legible please!
Do not use acronyms. Use structures whenever they are asked for, or appropriate. Your
explanations should be brief. Overly lengthy answers with irrelevant or erroneous
material will receive deductions. GOOD LUCK
1. (13 Pts total) Please answer the following questions about glycogen metabolism. Use
chemical structures where indicated.
a) 4 pts Draw the structure of glycogen, explaining all connection points between
carbohydrates.
b) 3 pts What is meant by reciprocal regulation? Give an example associated with
glycogen metabolism.
c) 6 pts Draw the mechanism of glycogen cleavage catalyzed by the relevant enzyme.
2. (30pts total) Outline the degradation of a five carbon number fatty acid, starting with
its activation (structure please). Please show all structures. The breakdown of this
molecule leaves a remnant that must be converted into another metabolite in two steps.
Both these steps require important cofactors. Draw the mechanism of these two steps.
3. (12 pts) What are the five general steps associated with signal transduction? Describe
specifically the first four of these steps for the signaling processes associated with
glycogen breakdown. You must put these steps in order. (You may show intermediate
steps if you wish.)
4. (12 Pts) Describe the process by which proteins are marked for degradation and then
degraded in cells. You must describe each of the required activities and state which
protein and/or complex is responsible for that activity. Show the relevant structures and
chemical reactions that take place. Please make sure to show the unique bond formed on
tagging and describe its structure. Why is this an unusual bond?
5. (8 Pts) Calculate the approximate yield in ATP molecules of the complete oxidation of
the C12 fatty acid shown below. (Show how you arrive at this number.)
6. (10 pts) Methionine is degraded to a four carbon molecule- outline the steps in this
conversion. What other amino acid is required for this transformation? What amino acid
is synthesized in this process?
7. (15 pts) The degradation of all branched chain amino acids have many common steps.
Choose one branched chain amino acid and outline its degradation (structures please) to a
common intermediate of another pathway. Please note when a step is similar to that
performed in a different pathway (i.e. not branched chain), and say what that is.
8. (20) There are two pathways for the degradation of serine. Outline (structures
required) these pathways, showing all reaction products. A cofactor that is ubiquitous in
amino acid metabolism is involved in a step in each of these pathways. Draw the
mechanisms for these two transformations.
9) Extra special credit 10 pts The pathway for urea formation has two energy intensive
steps, what are these? For the second of these steps, suggest a mechanism for the
reaction (you have not seen this mechanism in class.
Point breakdown
Possible
actual
1)
13
________
2)
30
________
3)
12
________
4)
12
________
5)
8
________
6)
10
________
7)
15
________
8)
20
________
9)
10
________
TOTAL 130
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