Final year, questions PDF

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Biology 200 Sample Final Exam Total time: 2.5 hours.

Section: _______________ Family Name: __________________ Given Name: __________________Student #: ___________ (please print)

Instructions: 1. Use black or blue PEN only. Exams that are written in pencil, or that have corrective tape on them will not be eligible for re-grading. 2. Answer all questions on this paper. No booklet is required for this exam 3. You are allowed an 8.5x11 inch, double-sided, hand-written memory aid for this exam. All memory aids that do not conform to these rules will be taken away. 4. You will have 75 minutes for this exam. 5. Please return all pages, including rough notes when you hand in your exam.

BIOL 200 Final Exam Marks Question Student Score Maximum Score

1

2

3

4

5

6

7

8

TOTAL

7

12

15

9

11

8

10

20

91

Page 1 of 11

Question 1. (____/ 7 marks) Chloroplasts, mitochondria, and nuclei are three intracellular organelles that are surrounded by two biological membranes. Although they possess some structural similarities, they have many differences in function and biogenesis. For statements 1 to 7 in the table below, indicate whether it applies to: A. Chloroplasts only B. Mitochondria only C. Nuclei only D. Both chloroplasts and mitochondria, but not nuclei E. All three organelles STATEMENT 1) These organelles contain remnant genomes carried on circular chromosomes, which reflect their evolutionary origins. 2) mRNA is transported through multi-protein complexes in the membranes surrounding this organelle to the cytoplasm for translation. 3) This organelle contains euchromatin and heterochromatin.

Fill letter A-E

4) The outer envelope membrane is continuous with the endoplasmic reticulum. 5) The outer envelope membrane, but not the inner envelope membrane, is porous and allows molecules to diffuse across freely. 6) The inner envelope membrane of this organelle is highly folded increasing its surface area. 7) This organelle contains an additional internal membrane system, in addition to the two membranes surrounding the organelle.

Page 2 of 11

Question 2. (____/ 12 marks) For each of the observations below, write a statement that could explain these results, based on what the data shows and on your knowledge of cellular structure/ function (3 marks each) A. If taxol is added to cells at metaphase, the chromosomes do not move towards the spindle poles in anaphase.

B. Electron micrographs show that mitochondria in heart muscle have a much higher density of cristae than mitochondria in skin cells.

C. Microtubules formed in vitro from tubulin that is bound to a non-hydrolyzable form of GTP were found to be exceptionally stable.

D. Some membrane proteins can be readily extracted with 1M NaCl, whereas others require the use of an organic solvent or detergent.

Page 3 of 11

Question 3. (____/15 marks) On the domain maps provided, draw and label all targeting sequences that you predict would be found in the proteins, A - E. If you predict no targeting sequence is required, clearly indicate this in your answer – a blank will NOT be considered for marks. (2 marks each): A. Soluble ER resident N-#

-C#

B. Rubisco Small Subunit 2B – a Chloroplast stromal protein N-#

-C#

C. Transcription factor N-#

-C#

D. α-tubulin N-#

-C#

E. Glycophorin A (plasma membrane protein), 1 transmembrane domain, N-terminus outside the cell. N-#

-C#

Match each of the proteins mentioned above with its cellular location, as identified in each micrograph (arrow) below. (1 mark each): Micrograph* Protein* (A-E)* 1*

!

2*

!

3*

!

4*

!

5*

!

Page 4 of 11

Question 4 (____/9 marks) The epidermal growth factor receptor (EGFR) is a transmembrane protein localized to the plasma membrane in skin epithelial cells. When EGFR is activated by binding to the extracellular peptide, EGF, it is internalized via vesicles. Ultimately, this internalization will lead to changes in cell growth and division. Researchers studied the relationship between EGFR internalization and cell growth by investigating wild type cells compared to cells with a non-functional mutant form of clathrin. A. The first experiment examined the amount of EGFR found in early endosomes in the wild type and mutant cells, in the absence (-EGF) or presence (+EGF) of the extracellular peptide. Describe the results shown, and explain what you can conclude based on these data. (3 marks)

B. In the next experiment, they examined the effect of EGFR internalization on cell cycle proteins, to see whether there were any changes. The SDS-PAGE data below shows the results for Mitotic Cyclin (M-Cyclin), a protein known to promote entry into mitosis, in the absence or presence of EGF. Describe the results, and explain what you can conclude based on the gel shown. (2 marks).

C. The researchers discovered that after the wild-type cells are exposed to EGF, a transcription factor (called ERK1/2) moves into the nucleus. On the other hand, ERK1/2 remained localized in the cytoplasm when the clathrin mutants were exposed to EGF. Considering this and the rest of the data in this question, propose a model describing how EGF-binding to EGFR might affect the cell cycle progression. In your explanation, include the role of EGF and its receptor, clathrin, the transcription factor ERK1/2 and Mitotic Cyclin. (4 marks)

Page 5 of 11

Question 5 (____/ 10 marks) Actin Capping Protein (ACP) binds to the plus end of actin filaments, preventing the actin filaments from gaining or losing monomers. Its activity is blocked by regulatory proteins such as V-1. In this experiment, Takeda et al. (2010) examine the role of V-1 and ACP in the regulation of actin polymerization. In Panel A, the ratio of F-actin (actin filaments) to G-actin (actin monomers) were measured for WT (normal) and V1 (over-expresses V-1) cells. In Panel B, actin filaments and nuclei were stained with fluorescent dyes and cells were examined through fluorescence and light microscopy. Assume that both cell lines express the same amount of ACP.

A. A. Compare the bars in the chart in Panel A. What do they tell you about the amount of actin in each cell type? How might the change in expression levels of V1 be affecting ACP’s ability to function? (3 marks).

B. Panel B shows paired brightfield and fluorescence microscopy images of each of the cell types measured in Panel A. Compare the shape of the WT cells to the V1 cells, and explain how the actin shown in the fluorescence images is contributing to that shape. (4 marks

C. Based on the data shown in Panels A and B, how might V-1 be influencing cell shape in the overexpressing cells? (3 marks)

Page 6 of 11

Question 6 (____/ 8 Marks) You generated a yeast strain with a temperature-sensitive mutated form of M-cyclin that is unable to fold stably at a non-permissive temperature (37°C). To assess its role in the cell cycle, you grow these mutant cells in a test tube at the permissive temperature (25°C) then shift them to 37°C. A. Explain what happens to M-cyclin concentration as the cell progresses thorough interphase at the permissive temperature. How does this compare at the non-permissive temperature? (2 marks)

B. What effect would this mutation have on the regulation of cell cycle at the non-permissive temperature (2 marks)?

C. You fluorescently labelled the DNA of your mutant yeast cells and used fluorescence activated cell sorting (FACS) to analyze the effect of this mutation on the cell cycle. Note that these cells complete a cell cycle in 90 minutes where interphase lasts for approximately 70 minutes. In your experiment, you have 2 tubes (labeled Tube 1 and Tube 2). In Tube 1, you incubate the yeast cells at the nonpermissive temperature, 37°C, for 2 hours. In Tube 2, you incubate the cells for 2 hours at nonpermissive temperature, followed by 30 minutes at the permissive temperature. In the appropriate spaces below, draw the expected FACS readout from each Tube and label the graphs with the relevant phase of cell cycle expected. FACS Readout for Tube 2

Number of cells

Number of cells

FACS Readout for Tube 1

Fluorescence intensity

Fluorescence intensity

Page 7 of 11

Question 6 (____/ 9 Marks) Nocodazole is used as an anti-cancer drug that binds to a/b tubulin subunits inside cells. Shown below are fluorescence images of cells in the presence or absence of nocodazole, after fluorescence immunolabeling of a-tubulin.

A. Describe the fluorescence pattern seen in Panels A and B. What does this tell us about the effect of nocodazole on microtubules? (3 marks) Describe the Fluorescence Pattern

The Effect of Nocodazole

Panel A

Panel B

B. Based on your knowledge of microtubule polymerization at the plus end, propose a model for how Nocodazole might be leading to the results shown. (2 mark)

C. Predict what would happen to the cell in Panel B if the nocodazole was washed away and the cell was allowed to recover. (1 mark)

D. Predict the impact of nocodazole treatment on constitutive secretion in these cells? Explain why. (2 marks)

E. Propose a role for nocodazole in the M-phase which makes it useful as an anti-cancer drug. (1 mark)

Page 8 of 11

Question 8 (Outline. 20 marks) Each organelle in the cell is a unique microenvironment where certain cellular functions are performed. Write an essay outline to critically assess the following statement: “The intracellular areas of low pH are essential to the function of some organelles.” Your arguments (and associated supporting evidence) should provide examples from 3 different organelles. Thesis statement: (1 sentence recommended, 2 sentences MAX) •

Score: _____/2 Argument 1 and evidence: (2 sentences recommended, 3 sentences MAX. 1 sentence per bullet) •

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•

Score: _____/4 Argument 2 and evidence: (2 sentences recommended, 3 sentences MAX. 1 sentence per bullet) •

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• Score: _____/4 Argument 3 on next page Page 9 of 11

Argument 3 and evidence: (2 sentences recommended, 3 sentences MAX. 1 sentence per bullet) •

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•

Score: _____/4

Essay Outline Organization: _____/6 Total Essay Outline Score: ______ /20

THE SPACE OUTSIDE OF THE BOXES WILL NOT BE MARKED

Page 10 of 11

THIS PAGE LEFT INTENTIONALLY BLANK – USE IT FOR ROUGH NOTES THIS PAGE SHOULD BE HANDED IN WITH THE REST OF YOUR EXAM

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