CHEM-342 Introduction to Biochemistry                Name ______________________________
Midterm Examination - Individual Part
Friday, 29 March 2002
H. B. White - Instructor

Important - Please read this before you turn the page.

Exam Statistics
                    Number of students                18            Ave.                        Range                (out of 80 points)
                    Number of groups                     5            Ave.    20.3             Range    17 - 23 (out of 30 points)
                    Class Totals                                            Ave.                        Range                 (out of 100 points)

Part II Three Short Answer Questions. (4 Points each)
1. Explain clearly why Zinoffsky's repeatedly crystallized horse hemoglobin until the elemental analysis of the mother liquor matched that of the crystals? (Here and elsewhere on this exam, pictures to augment words are especially welcome.)

2. Peters used ferricyanide to oxidize hemoglobin to methemoglobin and release the bound oxygen, which he measured as a gas. But, oxygen is soluble in water and was released from hemoglobin in solution. How is it possible to quantitatively measure oxygen volumetrically as a gas when some of it is dissolved in solution?

3. Venous blood contains deoxyhemoglobin. Where did the oxygen go? How is this similar to Stokes' experiment?

Part III Problems and Short Essays
1. (9 Points)
When Professor Essigsaure first tried to repeat the experiment in Section 11 of Stokes' article he was in a hurry (as usual) and tried to cut corners. As described, he added an equal volume of ether to his dilute solution of blood. Then he added the glacial acetic acid to the mixture until the color turned brown and mixed it gently until the hematin extracted into the ether phase. After washing the ether layer once, his patience began to wear.  Rather than washing the ether layer until the hematin precipitated at the interface, he went directly to the last step and added some bicarbonate solution expecting to have the hematin transfer into the aqueous layer. Fortunately, he was wearing lab goggles and protective gloves because the solution erupted in froth and overflowed the container spilling over his hands.
A. (3 Points) What is the purpose of washing the ether layer? Draw a picture or equation of what is happening.

B. (3 Points) Why did the solution erupt when the bicarbonate was added? Write an equation to help explain your answer.

C. (3 Points) Would the solution have erupted in froth had Prof. Essigsaure used a dilute ammonia solution rather than bicarbonate? Explain.

2. (10 Points)
Peters (1912) used an earlier version of what came to be known as the Warburg Constant Volume Manometer Apparatus shown below. The apparatus shows the appearance at the beginning of an experiment. Assume that an oxygen-generating reaction has occurred in the reaction vessel to produce some volume of gas.
A. (5 Points) Show how the clove oil would be displaced and how its level would be adjusted before a reading would be made?

Image copied from Umbreit, Burris, and Stauffer,  ManometricTechniques, 4th ed. 1964

 B. (5 Points) What properties does clove oil have that makes it particularly suitable as the displaced fluid in the manometer?

Part IV Essay (14 Points)
There are three quotations below reflecting various views of the nature of science. Select one to defend or refute using examples and evidence taken from the articles you have read so far this semester Stokes (1864), Zinoffsky (1886), Peters (1912), Conant (1923), and Svedberg & Fåhraeus (1926). Use the back of this page to organize your answer, if you need more room.

Progress in science depends on new techniques, new discoveries, and new ideas, probably in that order.                                                                                                               Sydney Brenner

…scientists love to do experiments that show their colleagues to be wrong. By this adversarial process, science gradually reveals the way nature works. The notion that published science must be free of errors, and that error itself indicates sloppy thinking or fraudulent intent, is misguided.
                                                                                                                         Robert Pollack

It is all too easy, for scientists and non scientists alike, to assume science produces truth. What it generally produces however, are models: deliberate in their assumptions, limited in their scope, provisional in their conclusions, and extraordinarily useful for certain purposes, even perhaps certain causes. But they are neither perfect, nor permanent.
                                                                                                                 Frank H. T. Rhodes

Part V Bonus (5 Points)
The arterial blood of a typical college student contains about 16g of Oxyhemoglobin per 100ml. Estimate how many ml of oxygen per 100ml of blood does that represent at standard temperature and pressure? (Note: Estimation does not require a calculator. Any answer within a factor of 2 is correct. Show work for credit.)

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Last updated: 29 March  2002 by Hal White
Copyright 2002, Department of Chemistry and Biochemistry, University of Delaware