CHEM-342 Introduction to Biochemistry                     Group Members________________________
Mid-term Examination - Group Part
Wednesday, 21 March 2001
H. B. White - Instructor

Important - Please read this before you turn the page.

1.    Like Zinoffsky, both Conant and Svedberg & Fåhraeus studied equine hemoglobin.
    A.    (2 points) Figure 1 of Conant’s article shows the reversible electrochemical titration of hemoglobin. What are the colors of his hemoglobin solutions at the end points of the titrations with ferricyanide and dithionite (hydrosulfite), respectively?

    B.    (2 points) Svedberg & Fåhraeus determined the molecular weight of two different forms of hemoglobin. What were the colors of each of these forms?

    C.    (3 points) Would the color of the hemoglobin solution be of any importance to the experiments by either Conant or Svedberg & Fåhraeus?


2.    (3 points each) State clearly in one sentence, the major conclusion/significance for each article.

    A.    Conant:
    B.    Svedberg & Fåhraeus:


3.    (6 points) Dr. Essigsaure is trying to repeat Conant’s experiment but he hasn’t fully mastered the technique. Halfway through a beautiful electrochemical titration with dithionite, his system developes a leak in which oxygen enters the system before he reseals it. Never the one to waste an opportunity, he continues the titration to the end point with the results shown below: Estimate the amount of oxygen (relative to total hemoglobin) that leaked into the cell.

                                                                        Volume of standardized dithionite

    4.    (6 points) Dr. Essigsaure loves to play in the lab but avoids calculations. A friend of his studies a type of worm that is "blood red," thinks they contain hemoglobin, and wants to find out its molecular weight. Every ready Essigsaure, cranks up the old analytical ultracentrifuge following Svedberg’s instructions and soon discovers that the protein is much larger than he expected. He keeps lowering the speed of the rotation until the concentration curve exactly matches the one shown in Svedberg and Fåhraeus’ article. After many trials in which a less persistent but more mathematically inclined scientist would have simply calculated the molecular weight or the appropriate rotational velocity, Dr. Essigsaure found that when the rotational speed was about 25% that of Svedberg and Fåhraeus, his concentration profile was as shown. What is the approximate molecular weight of the worm hemoglobin? What assumptions do you have to make?


Bonus Question (1 point) What does "Essigsaure" mean in German?

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Copyright 2001, Department of Chemistry and Biochemistry, University of Delaware