C485 Exam I Fall ‘14
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. (6 pts) Match the enzymes that degrade glycogen in the left column with the
appropriate properties in the right column. (More than one property may match. You
need to get each answer completely correct for credit.)
(a) Phosphorylase _______
(1) cleaves -1,4 glucosidic bonds
(b) -1,6-Glucosidase _______
(2) releases glucose
(c) Transferase _______
(3) releases glucose 1-phosphate
(4) moves three sugar residues from
one chain to another
(5) requires ATP
.
2. (12 Pts) Show the overall reaction for a complete photosynthetic process, showing both
ATP production and NADPH production (start with two water molecules and absorb as
many photons as necessary). Show the specific reactions for photosystem II and the
cytochrome bf complex.
1
Mechanisms 3-5!!!!!
3. (10 Pts) A basic carbon-carbon bond forming reaction in the pentose phosphate
pathway transfers two carbon fragments. Give an example of this reaction and draw its
mechanism. You may assume active site general acids and bases as necessary. Please
show the necessary parts of any cofactors. (YOU MUST USE STRUCTURES AND
ARROWS). Please use the back of the exam if necessary.
4. (14 pts) There are three basic types of carbon-carbon bond forming reactions in the
Calvin cycle. You have drawn the mechanism of one of these in problem 3. What are
the other carbon-carbon bond forming reactions in the Calvin cycle- give an example of
each (structures please). Draw the mechanism of these reactions. Please use the back of
the exam if necessary.
2
5. (10 pts) An unwanted side reaction occurs during the dark reactions of photosynthesis.
What is this reaction? Draw its mechanism. Under conditions of drought, this reaction
becomes much more prevalent. Why is this? Please use the back of the exam if
necessary.
6. (8 pts) What is structure of glutathione? Explain its role in red blood cells. How does
an important enzymopathy affects this function?
7. (8 Pts) Diagram the Q cycle and explain how this accounts for the stoichiometry of
proton pumping and uptake.
3
7. (8 pts) How is the Calvin cycle regulated? Explain the logic of this regulation.
8. (8 pts) Assume that a cell only needs to synthesize NADPH and not ribose. How can
this be done? (Brief explanation) Show the stoichiometry of this process showing the
maximum amount of NADPH that may be synthesized via the pentose phosphate
pathway.
9. (14 Pts) Your textbook describes the regeneration phase of the Calvin cycle as the
mirror image of the pentose phosphate pathway. Is this true? Where do these pathways
differ? What is the functional reason for why these pathways must differ, and how is this
accomplished.
4
10. (8 pts) Draw the mechanism for how the mobile electron carrier between PSII and
Cytochrome bf undergoes oxidation (use chemical structures).
11. Extra Credit (12 Pts) Energy yielding steps are often thermodynamically
unfavorable, so the cell links these to functionally irreversible steps, or steps that are well
downhill in energy. Give two examples of such steps from the pentose phosphate
pathway, and comment on whether they are similar to, or different from strategies used in
the Krebs Cycle.
5
Point breakdown
Possible
actual
1)
6
________
2)
12
________
3)
10
________
4)
14
________
5)
10
________
6)
8
________
7)
8
________
8)
8
________
9)
14
________
10)
8
________
EC) 12
________
TOTAL 110
___________
6