Wednesday 26 March 1997

7:30 - 9:00 p. m. 101C Pearson Hall

Instructor: Hal White

INSTRUCTIONS - Read them before you turn the page.

1. This examination has two parts. Complete the questions in Part I individually and turn in your answers by 9:00. If you finish early, you may leave the room until Part II, the group part, starts at 9. Part I is worth 75 points. Part II is worth 25 points. This examination will constitute 20% of your final grade.

2. You may refer to your notes, the course reader, handouts, and any homework assignments. Textbooks or other reference books are permitted for Part II of this examination, but not for Part I.

GRADING

While for some questions there is no single "right answer," some answers will be better than others. I will award better grades to answers that show a greater depth of understanding, use appropriate examples, and are written clearly and logically. I will be looking for high quality answers. Remember: Strive to write not that you may be understood, but rather that you cannot possibly be misunderstood. Stream of consciousness answers are rarely well organized or clearly presented.

Part I Individual work (75 points)

1. (20 points) The following short answer questions worth 4 points apiece are based on learning issues raised in different groups this semester.

A. What is potassium oxalate? How does it inhibit blood coagulation?

B. How does the presence of methemoglobin interfere with the measurement of oxygen binding by hemoglobin?

C. What is the source of carbon dioxide in the blood?

D. If reducing agents don't reduce hemoglobin, what do they reduce in Stokes' experiments?

E. If the elemental composition of a crystal and its associated mother liquor are not identical, does this mean that the crystals are impure?

Bonus (2 points) What is the partial pressure of oxygen (in mm of Hg) in air at standard temperature and pressure?

2. (15 points) Prof. Essigsauer returned to his lab one night to prepare for a lecture demonstration based on the experiment presented by Stokes in Section 11 of his 1864 article. Within minutes Prof. Essigsauer was looking high and low for the glacial acetic acid and mumbling angrily about associates who don't replace the things they use up. Frustrated, but undaunted, he figured any acid would do and substituted concentrated hydrochloric acid. After all, he reasoned, a stronger acid should work even better. -- Not so. Sure enough the hemoglobin solution turned brown immediately upon addition of HCl but, much to his initial puzzlement, the resulting hematin did not extract into the ether layer. Please explain in chemical terms why HCl cannot be substituted for glacial acetic acid in this experiment. Please feel free to draw chemical structures and diagrams to support your argument. If you are uncertain of the explanation, please outline the possibilities you would consider as explanations or how you analyzed the problem.

[An important objective of CHEM 342 is to create situations where you have to analyze, synthesize, and evaluate information. Part of the process of activating curiosity requires that you are aware of what you know, what you don't know, and what you need to find out in order to understand something.]

3. (25 points) Jaundice can indicate increased red cell lysis or hepatic disease. The compound shown below, and/or its diglucuronate conjugate, accumulate in the blood of jaundiced individuals.

A. What do you already know about this topic from other courses, general reading, or personal experience?

B. Identify at least 10 things that you don't know about this topic that might be worth knowing. Please phrase your responses in the form of specific questions (learning issues).

C. Of the learning issues listed in part B, identify two or three that you think are really important and explain on the back of this page why you would put them at the top of your list of things to learn more about.

4. (15 points) Models conceptualize and generalize information in ways that enable us to interpret the world around us and communicate that understanding to others. By necessity models are simplifications that emphasize certain things. They make predictions that lead to experiments whose results can refine, alter significantly, or even disprove a model. In the time since your group created a model of hemoglobin based on Stokes' 1864 article, you have read articles by Zinoffsky (1886) and by Bohr, Hasselbalch and Krogh (1904). In addition, we discussed as a class the results reported by Peters (1912), Douglas et al. (1912), Conant (1923), and Svedberg and Fåhraeus (1926).

[You and your group will answer this question again in Part II of this examination.]

A. Make a list below of the facts known about the chemistry of hemoglobin by 1926.

B. Construct a model that incorporates that information. You may make more than one model if certain ideas confuse the modeling of other ideas. Use the back of this page or a blank sheet of paper for your answer.

Instructions

Problem 4 from Part I will be answered again in Part II but with the benefit of group discussion and with access to reference books. Provided agreement is reached, each group will hand in a single answer to be graded. That grade will be added to your score on Part I. If you do not agree with your group's answer, you may hand in a separate answer which will be graded and used in place of your group's grade.

This part of the examination should end around 10:00 p. m. Any group or individual can stay longer, within reason. Class will not meet on Friday morning.

4. (25 points) Models conceptualize and generalize information in ways that enable us to interpret the world around us and communicate that understanding to others. By necessity models are simplifications that emphasize certain things. They make predictions that lead to experiments whose results can refine, alter significantly, or even disprove a model. In the time since your group created a model of hemoglobin based on Stokes' 1864 article, you have read articles by Zinoffsky (1886) and by Bohr, Hasselbalch and Krogh (1904). In addition, we discussed as a class the results reported by Peters (1912), Douglas et al. (1912), Conant (1923), and Svedberg and Fåhraeus (1926).

A. Make a list of the facts known about the chemistry of hemoglobin by 1926.

B. Construct a model that incorporates that information. You may make more than one model if certain ideas confuse the modeling of other ideas. Use a separate sheet of paper and have all participating group members sign it.

Your model for Part II B.