Dr. Reichler’s Bio 311C MWF 1-2pm Print
Exam #3 December 4, 2006
Read each question carefully and don’t hesitate to
ask if a question seems unclear. If possible, answer each
question in the space provided, but if needed, continue on the
back. If you use a drawing as part of your answer, be sure to
also include a written explanation. These questions have specific
answers, although for some, more than one answer is possible. To
receive full credit you must clearly and fully answer the question
being asked. This exam is worth 100 points with the points for
each question noted in parentheses.
1. Using rules 1 and 2 of Strong Inference, the parts prior to doing
experiments, answer the following question: What is the function
of IP3 in a cell? (8 pts)
Must use Strong Inference and make
multiple hypotheses and experiments to eliminate hypotheses.
Ex: hypo’s- It is an energy source. It has no
function. It is involved in calcium signals. Expt-
Eliminate IP3 and see if cell can make energy or transduce a calcium
2. The conversion of glutamic acid and ammonia to glutamine has a DG of
+3.4kcal/mol while the conversion of ATP to ADP and Pi has a DG of
–7.3kcal/mol. Why can one molecule of ATP not be used to produce
two molecules of glutamine? (6 pts)
Even though there is more than double
the energy released by ATP than is needed for the production of
glutamine, 3.4 x 2= 6.8kcal/mol. Energy transfer is never 100%
efficient. So the loss of energy to entropy will mean that one
ATP is needed for each production of glutamine.
3. The final product of photosynthesis is quickly consumed for the
plant’s metabolism, and some of the intermediate products are also
quickly consumed. If, under various conditions, you wanted to
measure the efficiency of photosynthesis, what would you measure, and
how would this measurement reflect photosynthetic efficiency? (6 pts)
Measure oxygen production.
Water is split to provide electrons to replace those liberated from
pigments after light is absorbed by the pigments.
4. What is the difference between what happens to the electrons after
the electron transport chain in photosynthesis and cellular
respiration? (8 pts)
In photosynthesis the electron is
accepted by NADPH. In cellular respiration the electron is
accepted by oxygen.
5. For each G3P produced by the Calvin cycle, how many total carbon
atoms moved through the cycle? Explain. (6 pts)
18. 3CO2’s added to 3 RuBP (5C)
= 18 carbons for each G3P.
6. Overall glycolysis is exergonic, but some of glycolysis is
endergonic. Explain. (6 pts)
Initially 2 ATPs are expended to
break down glucose, and then 4 ATPs are formed by substrate
7. What stimulus would a human cell need to respond to that would
involve a change in cellular respiration? Would this response
involve changes in DNA packaging? Why or why not? (6 pts)
Oxygen availability. Low oxygen
would meant that the cells would need to switch to lactic acid
fermentation. This will not involve changes in DNA
packaging. The cells need to make the switch rapidly.
What organic molecules are
available. Sugar, amino acids, fats, etc?
8. With regards to the final step in ATP production, what is one
similarity and one difference between the production of ATP in cellular
respiration and photosynthesis? (besides where they occur) (6 pts)
Any one of:
Similar- Both involve chemiosmosis of
protons through ATP synthase to produce ATP.
Different- Photosynthesis- makes all
of its ATP via ATP synthase; electron excited again in PSI;
Cellular respiration- also makes some
ATP via substrate phosphorylation; electron donated to oxygen;
9. Some responses to signal transduction involve changes in gene
expression. How can calcium be involved in the movement of the
signal from the exterior of the cell to the nucleus? (6 pts)
The release of IP3 by PhosphoLipase C
can diffuse into the cell activating calcium channels that then release
calcium thereby activating calcium sensitive proteins that can
eventually activate a transcription factor that will bind to a promoter
and activate gene expression.
10. Would two different cells responding differently to the same signal
express different genes? Why or why not? (6 pts)
Yes, they must have either different
receptors and/or different effectors leading to different signal
transduction and different responses.
11. The genes coding for two proteins “stopthepain” and “handcramp” are
both expressed in people during test taking. Would you expect
their promoters to be similar or different? Why? (8 pts)
Similar. Similar expression
likely involves the binding of similar transcription factors to similar
12. Bacteria do not have enhancers like in eukaryotic cells, but there
are still cases in bacteria in which a sequence thousands of
nucleotides away from the transcription start site can affect
transcription. Describe how, in bacteria, a sequence far away
from the start of transcription can affect transcription. (8 pts)
Any one of: Repressors are
coded for by genes away from the promoter where they can block the
binding of RNA polymerase. CAP is coded for by a gene away from
the promoter where it binds to increase the binding of RNA polymerase
as in the lac operon.
13. What are one similarity and two differences between DNA replication
on the leading and lagging strands? (6 pts)
Similarity (any one of)- Need RNA
primer. Start with Primase. Use ligase. Add
nucleotides at 3’ end. Reads template in 5’ direction.
Differences (any two of)
Leading strand: Continuous
replication. Need single primase, primer, ligase, DNA
polymerase. Follows helicase. No gap at end.
Lagging strand: Discontinuous
replication (Okazaki fragments). Need multiple primase, primer, ligase,
DNA polymerase. Moves away from helicase. Leaves gap at end.
14. Would you expect the histones adjacent to the gene that codes for
histones to be acetylated during DNA replication? Why or why not?
Yes. As more DNA is made, more
histones are needed. Acetylation of histones unpackages nearby
genes thereby increasing transcription.
15. If a gene on one sister chromatid has a mutation, would you expect
the gene on the other sister chromatid to have that same
mutation? Why or why not? (6 pts)
Any of: Yes, the DNA in sister
chromatids is replicated DNA so the sequences should be the same.
No, if the mutation occurred during