C485 Exam I Fall ‘12
Name___________________
Legible please!
Do not use acronyms unless instructed to do so. 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. Use the back of the page if you
need room. GOOD LUCK
1. (20 Pts) There are two general types of C-C bond-forming reactions in the pentose
phosphate pathway. Please draw an example (structures please) of each one and show
the mechanism (arrows required) of the transformation. You may assume active site
general acids and bases as necessary. Please show the necessary parts of any cofactors.
2. (15 pts) Outline the components of the three major constituents of the photochemical
system in plants. Show the direction of electron flow from each individual component to
the next one in the system. You should also show where the electrons ultimately wind up
at the end of the process. (You may use a Z scheme if you wish.) Acronyms are okay.
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3. (8 pts) Draw the mechanism for how the mobile electron carrier between PSII and
Cytochrome bf undergoes oxidation (use chemical structures).
4. (10 Pts) Schematically show proton release and uptake from the major components of
the photochemical system in plants. Make sure to show where the protons come from
and where they go (it may be helpful to use a diagram of the thylakoid to show this).
Please give accurate proton inventory for each component. Assume a complete
photochemical cycle.
5. (7 Pts) Draw the mechanism by which the Q cycle pumps protons. Make sure to
account for the proton inventory in question 4.
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6. (10 pts) Outline the oxidative segment of the pentose phosphate pathway (show
structures of all the compounds involved- you do not need to name the enzymes). What
provides the driving force for the oxidation steps of the pathway?
7. (8 pts) What molecules regulate the Calvin cycle? Explain the logic of this regulation.
8. (14 Pts) Draw the mechanism of the unwanted competing side reaction catalyzed by
rubisco. What is the ultimate fate of the abberant molecules produced in this process?
Why is this process referred to as photorespiration?
9. (8 Pts) The pentose phosphate pathway is adaptable to the requirements of the cell.
What are the four differing situations that the pathway is responsive to?
10. Extra Credit (10 Pts) The Calvin cycle contains a number of phosphate ester cleavage
and then forming reactions that are not found in the pentose phosphate pathway. This
might seem at first energetically wasteful. What is the fundamental difference between
the two pathways that requires these energetically costly steps? How do these steps help
the Calvin cycle carry out its fundamental purpose? (Be brief)
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Point breakdown
Possible
actual
1)
20
________
2)
15
________
3)
8
________
4)
10
________
5)
7
________
6)
10
________
7)
8
________
8)
14
________
9)
8
________
10)
10
________
TOTAL 110
___________
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