Cell Biology

Biology 308: Review 2                              November 2001



There are two possible due times for this review. A review turned in by Monday November 12, 2001 at 3:00pm will receive 1.5 bonus points.

All reviews must be received by  8:30am Tuesday November 13, 2001.


This is a closed-book, closed-note review. There is no time limit for taking the review. All answers must be typed. You may use a calculator if calculations are required. However, the steps behind any calculation must be included to receive full credit (can be hand-written). Any figures or graphs may be hand-drawn.


The questions are yours to keep. This page must be the first page of your answer packet. Fill out the information at the bottom and attach this page to the ones containing your answers. The top of each additional page in the packet should contain only your initials and the page number.


Your review period begins when you read any question within this packet.

You can contact me at kabernd@davidson.edu, x2889 (o), or xxxxxxx (h). Any calls to my home must occur before 9:00pm.



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This review was completed in ________hours


I turned in this review by 3pm Monday ___ , attended the Animal Phys. lecture ___, the Bioethics lecture ___, the Chemistry lecture ___



The review contains 16 questions worth a total of 100 points and 4.5 attendance bonus points.


Section 1:


X-linked nonspecific mental retardation is an inherited disease that is cause by mutations in a protein called Rab GDP dissociation inhibitor a (Rab GDI a). Rab GDI a is expressed in the central nervous system and mutations in this protein result in mental retardation as well as defects in neuronal development.


1)    What is the name of the monomeric subunits found in Rab GDI a? 2pt

2)    Given the function indicated by its name, where in the cell do you predict this protein would be found? (Be sure to explain your prediction) 4pt


While researching Rab GDI a you find that it is encoded by a 7500 nucleotide gene called XAP-4 and that the XAP-4 mRNA is 2500 nucleotides in length.


3)    Provide a well-labeled diagram depicting the regions fond within any gene. (Labeled diagram only. No definitions) 4pt

4)    Referring to your diagram as needed, explain the differences between the XAP-4 gene and the XAP-4 mRNA. (Account for all regions of a functional mRNA) 5pt


Ca2+ channels are also found in the central nervous system.


5)    Where in a neuron are Ca2+ channels found? 3pt

6)    What makes neuronal Ca2+ channels open? Why is this opening important for neuronal function? 6pt

7)    Compare and contrast the steps required to go from XAP-4 mRNA and Ca2+ channel mRNA to localized, functional Rab GDI a and Ca2+ channel proteins. Every detail of every process should not be included. For example if photosynthesis is involved it is sufficient to say “The first step in the processing of each of the mRNAs is photosynthesis in the chloroplast”. DO include salient information regarding targeting. 10pt

8)    According to the SNARE hypothesis what role do Rab proteins play in cellular transport? 5pt

9)    Describe an experiment that would test if Rab GDI a is involved in transcytotic fusion. Be sure to explain controls for your experiment. (Details such as incubation times and volumes are not necessary but be sure to include how you would be able to interpret your results) 8pt

10) Predict and explain the results for the experiment described in #9. 5pt








Section 2:

The level of sexual mating in yeast (yeast fertility) relies on the coordinated action of many cellular components. While working on your mutant characterization in lab you decide to ‘play with’ cellular components and determine the effect on mating.

11) Would each of the following conditions be predicted to increase, decrease or have no effect on yeast mating efficiency of otherwise ‘normal’ yeast? Be sure to explain your reasoning. (5pt each)

a)     Treatment of both cell types with taxol.

b)    A mutation in each cell type causing G actin to show an increased rate of ATP hydrolysis.

c)     A mutation in each cell type causing kinesin to show an increased level of ATP hydrolysis.


12) Given a yeast genetics lab, describe the experimental conditions that would test your predictions for one of the conditions mentioned in # 11. Include how the results would be assessed/interpetted. 8pt


Section 3:


Anthrax toxin is a complex containing three different proteins (PA, LF, and EF) that are secreted by the bacterium Bacillus anthracis. During an infection the secreted complex associates with proteins on mammalian cells and is endocytosed. After internalization anthrax toxin changes shape, PA forms a pore through the membrane and LF and EF are released into the cytosol. LF and EF then wreak havoc on the cell as EF disrupts adenylyl cyclase signaling and LF is a protease that cleaves cytosolic proteins. (This is the true mechanism of anthrax toxicity.)


13) What are three types of endocytosis performed by all cell types? (Name them, do not elaborate) 3pt

14) Hypothesize the type of endocytosis involved in the internalization of anthrax toxin. Be sure to provide support for a) why you chose this type and b) why you did not chose the other types. 9pt

15) Comparing anthrax toxin to our class examples of endocytosis, predict the cause of the shape change that activates PA. 5pt


Cholera toxin is also internalized by endocytosis. It then follows the retrograde transport pathway to the ER before exerting its toxic effects.


16) What cellular components would provide the ‘roads’ and ‘motors’ in the pathway followed by cholera toxin? (Explain) 8pt