Fall 1999 Biology 111 Exam #1 - Cellular Communications

There is no time limit on this test, though I have tried to design one that you should be able to complete within 2.5 hours, except for typing. You are not allowed to use your notes, old tests, the internet, or any books, nor are you allowed to discuss the test with anyone until all exams are turned in at 11:30 am on Monday September 20. EXAMS ARE DUE AT CLASS TIME ON MONDAY SEPTEMBER 20. You may use a calculator and/or ruler. The answers to the questions must be typed on a separate sheet of paper unless the question specifically says to write the answer in the space provided. If you do not write your answers in the appropriate location, I may not find them.

Please do not write or type your name on any page other than this cover page.

Staple all your pages (INCLUDING THE TEST PAGES) together when finished with the exam.

Write out the full pledge and sign:

How long did this exam take you to complete (excluding typing)?

Lab Questions:

4 pts.
1) I have to make a confession. The neutral red solution you used in lab the first week was not 1M but in fact it was 0.1% w/v. Furthermore, the MW for neutral red is not 100, it is really 87.5.

a) Tell me how we made 450 mL of this 0.1% w/v solution.

b) What is the molarity of the solution you made in the test tube during lab that was

4% v/v of the stock solution which we told you was 1M but now you know is

0.1%solution? So calculate the true molarity of your "4% v/v" solution.

6 pts.
2) There are two parts to this question, A and B, which go with the two graphs below. Tell me in "plain English" what experimental conditions could alter an enzyme's reaction such that when graphed, it looks like the solid lines below, compared to the dashed lines from an ideal experiment. For both A and B, explain why this altered condition would produce its new graph. Graphs A and B represent different parts to this question and they should be answered separately.

Lecture Questions:
6 pts.
3) A major tenet in biology is that form follows function. Give an example that illustrates this point on the cellular level. Explain how this example illustrates the point.

6 pts.
4) What are the chemical differences between starch, glycogen, and cellulose? What significance do these differences have in your daily life?

8 pts.

5) Explain how changing one amino acid in a G protein could change its overall function. In your answer, properly use the different terms that describe the levels of protein structure with regards to G proteins.

5 pts.
6) An international team has found estrogen can bind to two different receptors, called alpha and beta. When estrogen binds to its alpha receptor, genes are activated, while binding to the beta receptor inhibits gene activation. Hypothesize a molecular mechanism to explain how the same ligand could give two different signals.

10 pts.
7) a) What category of modulation is needed to activate glycogen phosphorylase and glycogen synthase?

b) Describe what a cell must do to activate each of these two enzymes.

c) Which event, or events, of your answers from part b above happens when you get

scared?

d) What does the enzyme phosphorylase kinase do in your liver and how is it

activated?

e) What does the enzyme protein kinase A do in your liver and how is it activated?

6 pts.
8) In the space below, draw a picture of cAMP. In your drawing, you do not have to draw the base, simply write the letter that represents the base.

HERE ->

5 pts.
9) Tell me exactly what role ATP plays in pumping calcium ions across the SER membrane. I want you to be very specific and not say something general like "it provides energy." Tell me exactly which steps in the pumping cycle it facilitates and how.

15 pts.
10) Create a table with 3 columns in it and many rows (this can be a hand-drawn table if you don’t know how to create a table with your word processor). In this table, list as many examples as you can think of that we have studied so far. For each row provide the following information:

Column A: a mechanism where calcium ions were used in intracellular communication

Column B: where the calcium ions came from for each example in column A

Column C: What protein allowed it to cross a membrane and go down its concentration gradient for each example in column A and B.

6 pts.
11) How is resting membrane potential created? In your answer, include the structure of the plasma membrane, the protein responsible for generating the potential, and the ion or ions involved.

8 pts.
12) What happens at a presynaptic terminus that allows the neurotransmitter to be secreted? Start your explanation AFTER the action potential has reached the terminus.

6 pts.
13) How can the fertilization signal be deactivated within the egg? To receive full credit for this question, you must describe three different mechanisms for deactivation.

4 pts.
14) As explained in one of the study questions, many cancer researchers study signal transduction. G proteins are very important in many cancers because mutated G proteins cannot hydrolyze GTP.

a) Explain to me in "plain English" what the phrase "hydrolyze GTP" means.

b) Explain why this inability to hydrolyze GTP might lead to cancer.

5 pts.
15) Some forms of breast cancer are stimulated by estrogen. Design an experiment to determine if these breast cancer cells have more estrogen receptors or fewer estrogen receptors than healthy breast cells.

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