BIO 111, Fall 2000

Review 1 - Cellular Communication

Answer Questions 1-3 and 5 of the remaining 7 questions.

Provide thorough, but concise, answers.
There is no time limit to this test, but it should not take you more than 2 hours to complete.
The review is closed book.
Calculators are permitted.
All questions are worth twenty points
Please staple all pages together and do not put your name on any page other than this cover page.
Return completed review to me no later than 10:30 am, Wednesday September 20, 2000.

Name (please print):

Pledge and signature:


Answer Questions 1 - 3

1. A. How would you make 350 milliliters of 600mM NaCl? What percent solution is this? Hint: the molecular weight of NaCl is 58.5 and the molecular weight of water is 18.0.

B. How would you make 400 milliliters of 50% ethanol if you were starting with a solution of 70% ethanol? Hint: the molecular weight of ethanol is 46.0 

2. Wildcatase catalyzes the conversion of wildcat to wild. It has been shown that wildcat absorbs maximally at 405nm, while wild absorbs maximally at 490nm. The following graph shows the absorbance at 490nm over time of reactions containing constant amounts of wildcatase and various concentrations of wildcat.

    1. Explain this graph
    2. Describe what the graph probably would look like if measurements were made for an additional 15 minutes. Explain.
    3. To this graph, add lines representing data for reactions containing greater concentrations of wildcat. Explain.


3. You discover that an inconsiderate member of your lab group has broken the 490nm filter on the spectrophotometer. Describe an alternative method, still using the spectrophotometer, that you could use to investigate wildcatase activity. Draw a graph showing what your results probably would look like.

Answer 5 of the following 7 questions

4. The attached sheet shows the chemical structures of all twenty amino acids. Which amino acids can be phosphorylated? Explain your answer.

5. A. In general terms, explain how a ligand can alter the function of its receptor. Provide a specific example.
B. In general terms, explain how phosphorylation can alter the function of an enzyme. Provide a specific example. 

6. An important aspect of any cell communication system is the ability of the cell to terminate a signal. For one of the pathways we discussed, describe all the mechanisms by which the signal can be terminated. 

7. What is the most widely accepted theory for the origin of eukaryotic cells? Provide evidence supporting this theory.

8. Draw a graph that shows the change in membrane potential in a neuron during an action potential. Describe the state of various ion channels during this event.

9. Ca2+ serves as an important second messenger in several different signaling systems. Describe two events regulated by changes in intracellular Ca2+ levels. How does the cell control intracellular Ca2+ levels? 

10. Explain what the ‘fluid mosaic model’ of the cell membrane means. What major constraint does this model place on intercellular communication? In general terms, describe how integral membrane proteins allow cells to circumvent this constraint.