C485 Exam II Fall ‘14
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. (15 Pts total) Please answer the following questions about glycogen metabolism. Use
chemical structures where indicated.
a) 8 pts How many enzymatic activities are required for glycogen synthesis? Briefly
explain each one.
b) 3 pts What is meant by reciprocal regulation? Give an example associated with
glycogen metabolism.
c) 4 pts Draw the mechanism of glycogen cleavage catalyzed by the relevant enzyme.
2. (21 pts) Pick a branched chain amino acid. Draw the pathway for its degradation.
Draw the mechanisms of the first two steps of this pathway.
3. (12 pts) What are the five general steps associated with signal transduction? Briefly
describe (a) the hormone process that initiates the breakdown of glycogen; (b) the
hormone process that stimulates the synthesis of glycogen and absorption of glucose. A
good diagram for each will be useful.
4. (10 Pts) What tag is used to label proteins for degradation? Show the first enzymatic
reaction used to activate and form this tag. Comment on the energy requirements for this
reaction. Why is this necessary?
5. (18 Pts) List all the enzyme activities (including transport) required to degrade the C14
fatty acid shown below (either show the reaction at least once, or describe it). Calculate
the approximate yield in ATP molecules of the complete oxidation of this molecule.
(Show how you arrive at this number.)
6. (12 pts) What are the differences between fatty acid synthesis and breakdown? Given
these differences, how does the cell provide AcCoA for synthesis? How does it produce
the required reducing equivalents? Be specific and show relevant reactions (structures).
7. (6 pts) Describe how allosteric affects are used to regulate glycogen breakdown in
muscle. Explain why this makes sense given normal energy utilization in muscle.
8. (6pts) Outline the degradation pathway for proline.
9) (16 pts) Odd carbon number fatty acids leave a breakdown product that is different
than that formed from even number fatty acids. What is it? Show how this can be
converted into something that can enter a primary metabolic pathway. Draw the
mechanism of this/these steps.
10. (12 pts) super duper extra extra credit. It is often said that the urea cycle is coupled to
the Krebs cycle. In what way are these two pathways coupled? Why might this be
advantageous, and how does that explain the source of at least one of the nitrogens in
urea?
Point breakdown
Possible
actual
1)
15
________
2)
21
________
3)
12
________
4)
10
________
5)
18
________
6)
12
________
7)
6
________
8)
6
________
9)
16
________
10)
12
________
TOTAL 128
__________