BCH/PPA 609 3 section exam April 9, 2004

Name _______________________
BCH/PPA 609 3rd section exam April 9, 2004
You only need to answer 6 of the following 7 questions.
1. Give the biochemical reactions of starch catabolism (in plants which is essentially the same as
catabolism of starch in humans) and compare this to metabolism of soluble fiber in humans.
How does this affect the nutritional quality of these carbohydrates? (6 points)
2. Give the C12 fatty acid (12:0; common name lauric acid; chemical name dodecanoic acid)
labeling pattern made in plant tissues by standard fatty acid biosynthesis [fatty acid synthase
(FAS) complex] versus the -ketoacid elongation (-KAE) pathway from [2-14C]-acetate.
(10 points)
Name _______________________
3. Indicate where in -linolenic acid (18:3; octadecatrienoic acid), 12-oxo-phytodienoic acid (12oxo-PDA) and methyl jasmonate you would find the labeled carbon starting from [1-14C]-lauric
acid. [It would be helpful if you pointed this out on structures you draw of these 3 molecules.]
(10 points)
[1-14C]-lauric acid:
Name _______________________
4. Erythrose-4-phosphate (E4P) is an intermediate sugar phosphate of the Calvin cycle. Give the
names and structures of the compounds E4P is made from and the products it is converted to in
this cycle of the dark reactions of photosynthesis. What would be the consequences of inhibiting
the conversion E4P into its products of the Calvin cycle? (10 points)
5. Compare and contrast the structures of cellulose, hemicellulose (cross-linking glycans) and
pectin. How do these structural differences affect their physical properties. (10 points)
Name _______________________
6. What were the phenotypic consequences of the act1 mutation in Arabidopsis and how did this
affect prokaryotic and eukaryotic lipid biosynthesis (Act1 encodes a plastid glycerol-3-phosphate
acyltransferase or GPAT). (10 points)
7. Only six enzymatic reactions are needed to convert CO2 to 1-deoxy-D-xylulose-5-phosphate
(DXP) of plastid isoprenoid biosynthesis. Give the structures of the substrates and products of
each of these six reactions including DXP. What would be the consequences of a null mutation
in the gene encoding 1-deoxy-D-xylulose-5-phosphate synthase, the enzyme catalyzing DXP
synthesis? (10 points)