C485 Exam IV Fall ‘12
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. (12 Pts) Draw the structure of isopentenyl pyrophosphate and outline its biosynthesis
from AcCoA. You must use structure.
2. (15pts) There are three basic biosynthetic strategies for the synthesis of phospholipids.
Starting with phosphatidic acid outline these pathways. Please account for the energetic
requirement of synthesizing the phosphodiester bond. You must use structures and
provide a specific example for each pathway.
3. (12 pts) Show the reaction catalyzed by aromatase. Draw a mechanism for creation
of the reactive iron species that carries out the first reaction. Draw the likely
intermediates in the reaction, and the mechanism by which the molecule is aromatized in
the final step.
4..(15 pts) List the three most important metabolic junctions. Diagram the like fate of
these molecules.
5. (10 pts) Describe the differences between agonists and antagonists. When would you
want a drug to act as an agonist? An antagonist? Is tamoxifen an agonist, or an
antagonist?
6. (16 pts) Draw the degradative pathway for the coversion of AMP and GMP to uric
acid. A defect in the degradative pathway for adenosine results in a condition known as
SCIDS. What is this defect? When this step operates normally, what is the
thermodynamic driving force?
7. (16 pts) Starting with palmitoylCoA, draw the biosynthesis of ceramide. You must
use structures and show the mechanism of the first step of this pathway.
8. (12 Pts) Starting with cholesterol, outline the biosynthesis of the major sex hormones
(estrogen and testosterone). You must use structures. What are the actual sex hormones
that are most active in stimulating a receptor response? Explain how receptors might
differentiate between two molecules that are so similar.
9. (8pts) Explain the regulatory strategy used to control purine biosynthesis. Make sure
you specifically state which reaction is affected, and what is causing the effect. Explain
the rationale for this type of effect.
Point breakdown
Possible
actual
1)
12
________
2)
15
________
3)
12
________
4)
15
________
5)
10
________
6)
16
________
7)
16
________
8)
12
________
9)
8
________
TOTAL 116
________