Cell Biology

Biology 308: Review 1                                  September 2000



The review is due Friday September 29th, 2000 at 3:00pm


This is a closed-book, closed-note review. There is no time limit for taking the review but it was designed to be completed in 2 hours. All answers must be typed and must be in the form of complete sentences unless the question specifically states otherwise. 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 does not begin until you read any question within this packet.


Any questions about the review should be directed to me at kabernd@davidson.edu, 894-2889 (o), or XXX(h). Any calls to my home must occur before 9:00pm.


Name: ____________________________________




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My signature indicates that I have completed this review following the Honor Code.


This review was completed in ________hours


Cell Biology Bio308                         Review 1                                        September 2000

Due by Friday September 29, 2000 at 3pm in Watson289



Answer all of the questions for each of the three scenarios that follow. There are 100 points and 5.5 bonus points on the review.


Senario1 Questions a-k, 39pt total

While in Australia for the summer Olympics you learn that the male platypus is the only venomous mammal. Intrigued you decide to devote your life to researching this unique animal. Fascinated by the fact that the platypus venom gland can secrete large quantities of a combination of peptides that cause severe pain, you focus your research on the venom producing cells in this gland.


1a) What is a peptide? Your definition should include the type of component(s) found in a peptide and how they are joined. (4pt)

            For 1pt bonus draw 2 of the components and the bond between them.


Your first experiment involves preparing slides of the venom producing cells and examining them by microscopy.


1b) Your microscope contains Zeiss brand optics and has two 10x oculars and an 80x objective. The condenser set at approximately 8mm below the stage for bright field microscopy. What is the total magnification of the sample? (3pt)

On your answer sheet include how you determined the magnification. Handwritten calculations are acceptable. The answer need not be in sentence form.

1c) Would you expect the venom producing cells to have all the same organelles as a leg muscle cell? (Explain) (3pt)

1d) Which organelles, if any, may be over-represented in venom producing cells? In leg muscle cells?  (Explain) (5pt)


After completing your histological studies you decide to examine the cells at the molecular level. You lyse (break open) the cells and use centrifugation to isolate intact nuclei.


1e) Our yeast RNA isolation protocol included lysing the cells and resulted in intact yeast nuclei in one of the pellets. (We weren’t interested in the nuclei so we discarded them and isolated nucleotides from the cytosol) Which cell type would be more difficult to lyse a venom gland cell or a yeast cell? (Support your answer) (4pt)




An Australian researcher emails you about a new hormone receptor found in platypus venom secreting cells. He says that he found the receptor in an intact nuclei preparation and thus concluded that the receptor is a protein found in the nucleus


1f) Do you agree with his conclusion or do you send him an email suggesting that he check his nuclei preparation for contaminating membranes? (Explain your response) (3pt)

1g) What types of membrane association can a protein have? Which type would you predict for this receptor? (and why) (5pt)

1h) How could you test your hypothesis (from 1g) experimentally?  Technique names are sufficient (do not need to include details like volumes or incubation times). Be sure to include how you would interpret your results. (5pt)

1i) Given the type of membrane association chosen in 1g, briefly discuss any secondary structure is necessary for that kind of association. Well-labeled diagrams may be used but be sure to include written explanation in sentence format)(4pt)


The platypus venom gland releases active venom into a duct that expends out through a fang-like process behind the animal’s hind leg. (really, this is true)


1k) Why doesn’t the platypus suffer from constant pain due to interactions between the venom and the cells that line the venom duct? (3pt)



Scenario 2 (Questions a-f, 22pt total)


Ima Student came to me with questions about yeast mating. 3 weeks ago she and her lab partners had performed a test to qualitatively measure yeast mating. Her lab notes for those experiments follow.


Bio308            Complementation Test

Strains: a leu auxotroph     Plates available: -lys d.o.,  -leu d.o., YEPD, -lys,-leu d.o.

              a lys auxotroph

Cells grew in YEPD liquid media. Mixed 10ul each cell type called it a+a. Spotted 10ul of cell on the plates. Grew for 2 days. Came back and looked at plate with Iwanna B. Enlab (lab partner)


Cell type




a cells




a cells




a + a cells





When we cam back decided needed way to compare amounts of growth we saw

            +++ à lots of growth in spot

            ++ à moderate growth in spot

            + à Minimal growth in spot

-       à no growth seen

Filled in chart on the previous page using these comparisons


????? Chart makes no sense! Arrgh!


2a) What is the ‘religious sounding’ name given to yeast by early brewers? (2pt)

For 1.5 bonus points what is the Latin name of the yeast we are using? (genus and species)

2b) What results would you predict for a complementation test between these two strains? (3pt)

2c) Provide a hypothesis to explain Ima and Iwanna's results. (4pt)

2d) Considering all you have read and discovered about the yeast mating reaction to which type of human extra cellular signaling is it most analogous? (and why) (3pt)

2e) The paper by Bowling et al. used a Northern blot to support that cpr1 had an effect on the ‘normal’ PR pathway. What are the differences in results from a dot blot (like our lab prepared samples for) and a Northern blot (like they performed)? Are those differences important to the point they were trying to make or could they have done a dot blot? (6pt)

2f) Bowling et al. report that a mutation in the cpr1 DNA results in large difference in the plant’s biochemical response to pathogens. But biochemical pathways are ‘run’ by proteins. In the most general of terms how does a mutation in a DNA result in a change in a biochemical pathway? (4pt)


Scenario 3 (Questions a-h, 39pt total)


You are a surgeon. Recently you removed the appendix of a 25-year-old Caucasian male. It was a standard and uneventful procedure taking about 30minutes. As usual the patient was under general anesthesia, he received a transfusion of 1pint of type O blood, remained in recovery for 2 hours and was released that afternoon showing normal vital signs. However, one week later during a follow up visit, the man complains of odd new symptoms that sound like Hashimoto’s thyroiditis (HT). You check your medical school texts to confirm that HT is an autoimmune disease resulting in hypothyroidism.


3a) What is an autoimmune disease? (3pt)


You order blood work to support your diagnosis. You ask the lab for the standard thyroid screen, which includes measuring levels of T4, TRH, TSI and TSH.


3b) On your answer sheet list the term that best describes predicted outcome of the blood work if the man has HT. List only the term. Terms can be used more than once. (8pt)


Terms: Increased, Normal, Decreased, Not applicable to this diagnosis (n/a)          

            Blood test:      T4 levels _____________

                                    TRH levels ____________

                                    TSI levels _____________

                                    TSH levels ____________


Once the blood work confirms your diagnosis, you tell the man how to treat his symptoms and send him home. When he returns for more blood work three weeks later, all symptoms are gone and all thyroid related hormones have returned to normal levels.


3c) How do you explain the transient nature of his symptoms? (3pt)

3d) Describe the type of extracellular signaling that is directly responsible for activation of a normal thyroid. (4pt)

3e) How could an autoimmune disease cause the hypothyroidism seen in HT? (5pt)

3f) Normal thyroid stimulation and the mating response in yeast rely on intracellular signaling pathways that are very similar. Given this background briefly outline the steps involved in the pathway that activates the yeast mating response. Include the type of receptor and types of components in the pathway. (6pt)

3g) Name 3 kinds of 2nd messengers. Include the 2nd messenger that is important for release of calcium ions from the ER (and indicate which one that is). (5pt)

For 1 bonus points each draw the chemical structures of 3 second messengers

3h) Discuss characteristics shared by the 2nd messengers named in 3g and how those characteristics are important for 2nd messenger function. (5pt)


Footnote: Hashimoto’s thyroiditis is an autoimmune disorder affecting the thyroid. Also the Platypus is the only known venomous mammal but specifics about the venom and the new steroid receptor were designed solely for the purpose of this review.