BCH/PLS/PPA 609 3 rd section exam May 3, 2007
Each question is worth a total of 17 points.
Name _______________________
(85 points)
1.
Describe the major plant cell wall polymers and their interactions. Include the general structural and functional features of the principal cell wall components and the differences between primary and secondary cell walls.
1

Name _______________________
2.
Compare the synthesis and accumulation of starch and fructans giving all steps starting with CO
2
fixation into 3-carbon acids by Rubisco. (10 points)
As you may recall fructans are soluble fiber (no calories and provides beneficial effects on the digestive system and can reduce adsorption of undesirable dietary components such as cholesterol) in the human diet and therefore soluble fiber is highly desirable in diets of well fed people. [Food companies are already incorporating fructans into health foods.] It therefore would be very valuable to genetically engineer rice (or another starchy food such as potatoes) to accumulate fructans in place of starch. Describe what enzymes you would up and down regulate to achieve this. (7 points)
2

Name _______________________
3.
The main saturated fatty acid made in plant tissues is octadecanoic acid which has 18 carbons and zero double bonds and is therefore commonly abbreviated as 18:0. 18:0 does not accumulate in plant cell membranes but instead is mostly desaturated to unsaturated fatty acid derivatives. Give the structure of two of the three main unsaturated fatty acids that are synthesized and accumulate in plant cell membranes and describe how this affects membrane structure and function. (8 points)
Consider that you are given the task of genetically engineering Arabidopsis for increased triacylglycerol accumulation in seeds at the expense of seed carbohydrate. List the enzymatic steps you would change and how you would change them. (9 points)
3

Name _______________________
4. Place the 10 amino acids missing from the diagram below illustrating the biosynthetic relationships of principal amino acids in plants. You can use the whole name or the 3 or
1 letter amino acid codes if you like. Circle or list the six amino acids that are of greatest importance as precursors for synthesis of alkaloids in plants. (17 points)
4

Name _______________________
5.
Answer the following three questions from required reading assignments: a.
Eckardt, N.A. 2005. Peroxisomal Citrate Synthase Provides Exit Route from Fatty
Acid Metabolism in Oilseeds. Plant Cell 17: 1863-1865.
1) What are some of the metabolic consequences of null mutants of peroxisomal citrate synthase? (4 points)
2) Mitochondrial respiration in senescing leaves is also supported by fatty acid

-oxidation. What are the major sources of fatty acids for this energy generation in leaves? (3 points)
5

Name _______________________ b.
Schardl, C. L., R. B. Grossman, P. Nagabhyru, J. R. Faulkner and U. P. Mallik
2007. Loline alkaloids: Currencies of mutualism. Phytochemistry 68 : 980-996.
General loline structures are:
1) The mutualistic symbiosis of fescue ( Lolium spp.) with the fungal endophyte, Neotyphodium ceonophialum , provides benefits to both organisms that are greater than the costs of the symbiosis. What might some of these benefits be? (3 points)
2)
3)
What are some of the metabolic costs of the bioynthesis of lolines. (4 points)
Give some of the methods Schardl et al. (2007) describe for determining the biosynthesis of the loline alkaloids made in endophyte infected fescue. (3 points)
6