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) The compound shown below is an intermediate in the biosynthesis of
cholesterol that is derived from HMGCoA. Outline the biosynthesis of this compound
from HMGCoA and show the mechanism by which the ten carbon compound is
conjoined from its precursors.
2. (10pts) Outline (structures) the biosynthesis of CTP from carbohydrate and simple
(amino acids or one carbon unit) precursors.
3. (12 pts) Outline (structures) the three major methods for the biosynthesis of
phospholipids (from glycerol). Make sure you show all activating agents and the
structure of any activated intermediates.
4. (16 pts) Thymidilate synthase (TS) and dihydrofolate reductase are important cancer
targets. Why? Draw the mechanism of TS and explain (using structures and words) how
fluorouracil inhibits this enzymes.
5. (8 pts) Show the origin of all the N, and C atoms of histidine.
6. (14 pts) Draw the biosynthesis of lysine. In one step, a one carbon fragment is lost.
Draw the mechanism of this step. (You may start with cofactor-bound substrate and end
with cofactor-bound product.)
7. (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?
8. (10 pts) Draw the mechanism of ribonucleotide reductase. What provides the reducing
power for this reaction? How is this reducing power transferred to the enzyme? (i.e.What
are the redox active molecules.)
9. (12 Pts) Outline the biosynthesis of the following: Ornithine. Asparagine. Serine.
10. (10pts) Describe three regulatory strategies used to control amino acid biosynthesis.
(In general terms)
Point breakdown
Possible
actual
1)
12
________
2)
10
________
3)
12
________
4)
16
________
5)
8
________
6)
14
________
7)
16
________
8)
10
________
9)
12
________
10)
10
________
TOTAL 120
________