Name _______________________
BCH/PLS/PPA 609 3rd section exam May 4, 2006
(85 points)
Answer five or all six of the following questions. If you answer all six questions your answer
with the lowest score will be dropped. Each question is worth a total of 17 points.
1. Describe the nitrogen (N) cycle in biology. How are the major forms of N used in
biochemistry usually formed and what are the forms usually utilized by plants? (11
points)
Recently the development of corn (Zea mays) with improved nitrogen use efficiency has
been announced. Briefly describe your hypotheses as to how this might have been
achieved based on your knowledge of plant biochemistry. (6 points)
Name _______________________
2. There are 15 reactions and 13 intermediate molecules in the Calvin cycle. Give the
structures of the pathway intermediates starting with the CO2 addition to RUBP by
RUBISCO. Don’t worry about precise stereochemistry of the structures (15 points)
To help you with this the structures and names of RUBP, a five, a four and a seven carbon
intermediate are given (Pi represents phosphate, PO42-):
H
C
O
C
O
HO
C
H
H
C
OH
H
C
OH
H
C
OH
H
C
O
H
Pi
H
H
C
O
Pi H
C
O
H
C
O
C
O
H
C
OH
O
H
C
OH
H
C
OH
H
C
OH
H
C
OH
H
C
OH
H
C
OH
H
C
O
Pi H
C
O
Pi H
C
O
Pi
Pi
H
H
RUBP
H
Ribose-5-P
H
Erythrose-4-P
Seduheptulose-1,7bisphosphate
Provide the structure of a major molecule providing carbon export (photosynthate) from
chloroplasts of photosynthetically active leaves. (2 points)
Name _______________________
3. Give labeling pattern of a six carbon fatty acid and the intermediates from
a. 1-14C-acetate and
b. 2-14C-acetate
of both the -ketoacid elongation (-KAE) and regular fatty synthesis pathways (13
points)
How would you determine whether a fatty acid in a plant tissue was synthesized from the
-KAE or regular fatty synthesis pathway? (4 points)
Name _______________________
4. Describe all steps you might want to change to ensure the selective accumulation of
hexadecatrienoic acid (16:3) made in the plastids in storage triacylglycerol in oil bodies.
i.e. Ensuring that 16:3 made in plastids accumulates to high levels in oil bodies but not in
plastids where it is initially synthesized. (12 points)
What is the chemical name of this detergent commonly used in polyacrylamide gel
(PAGE) electrophoresis, toothpaste and many other applications. (2 points)
O
Na+ O-
S
O
Na+O-
Give the structure of cis-9-octadecenoic acid, oleic acid, the main component of olive
oil. (3 points)
Name _______________________
5. Describe the steps from fixation of nitrogen gas, N2, into asparagine for export from
nitrogen fixing nodules. You can give names or structures of the molecules; its not
necessary that you remember both. (7 points)
Name _______________________
Amino acids can be placed into six groups depending on the carbohydrate precursors of
their carbon skeletons.
Place each of the 20 protein amino acids into one the following most appropriate groups:
(10 points)
Erythrose-4-P
Oxaloacetate
P-glycolate
Ribose-5-P
Pyruvate
-keto (=2-oxo)-glutarate
Name _______________________
6. Answer the following three questions from required reading assignments:
a. Wheeler, G.L., M.A. Jones and N. Smirnoff. 1998. The biosynthetic pathway of vitamin C in
higher plants. Nature 393: 365-369.
What are the key differences in ascorbic acid synthesis in plants compared to animals? (5 points)
b. Ding, S.Y., and M.E. Himmel. 2006. The Maize Primary Cell Wall Microfibril: A New Model
Derived from Direct Visualization. J. Agric. Food Chem. 54:597-606
Give a model of the maize primary cell wall microfibril. (5 points)
c. Scheible, W.-R., R. Morcuende, T. Czechowski, C. Fritz, D. Osuna, N. Palacios-Rojas, D.
Schindelasch, O. Thimm, M.K. Udvardi, and M. Stitt. 2004. Genome-Wide Reprogramming of
Primary and Secondary Metabolism, Protein Synthesis, Cellular Growth Processes, and the
Regulatory Infrastructure of Arabidopsis in Response to Nitrogen. Plant Physiol. 136: 2483-2499.
Describe the major metabolic changes that occur in response to changes in nitrogen status (7
points)