Cumulative Exam Questions

Cumulative Exam Questions - E1-1 Without using a...

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E1-1 Without using a calculator, show how you would determine the difference in [H + ] between two solutions of pH 4.5 and pH 5.4. How would you figure out the [H + ] values corresponding to each of these pH values? Show your work. A mother arrives at the emergency room with her child, who is in a lethargic state and panting with rapid shallow breaths. The child had gotten into the medicine cabinet and consumed many tablets of aspirin; as little as 3 grams can be fatal to a child. You are the physician on duty, and remember that an effective treatment may be to provide bicarbonate intravenously, to help lower the acidity of the child’s blood, which has just been measured to be pH 7.0. Based on the child’s height and weight, you estimate the total blood volume to be 2.0 liters, and blood gas measurements to have just given you a serum bicarbonate concentration of 20mM. You also recall that the pKa of carbonic acid is pH 6.4. Write the chemical equation for the dissociation of carbonic acid to bicarbonate. Before any further treatment, what is the ratio of bicarbonate to carbonic acid in the child’s bloodstream? Show how you arrive at your answer. If you wish to raise the pH to 7.4, what ratio of bicarbonate: carbonic acid should you aim for? From this number, how much bicarbonate (in moles or millimoles) should you give this child? Assume that all of the added bicarbonate gets into the bloodstream effectively and that there are on other buffering components in the blood. Finally, to set up the IV drip, you go to the refrigerator and retrieve a cold 1 liter sterile bag of 4M sodium bicarbonate. What volume of this will need to be administered to raise the child’s serum pH to 7.4? 1
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E1-2 Starting from the definition of the equilibrium constant, show how the Henderson-Hasselbalch equation is derived. Determine what the ratio of conjugate base [A - ] to undissociated acid [HA] will be if the solution is 0.6 pH units below the pKa of the acid. What will the pH be if this ratio is 8:1? Show your work. Sketch the titration curve of strong acid with base, and the similar titration curve of a weak acid. Why is this one, but not the other, capable of being an excellent buffer? Why would a solution of acetic acid alone in water, with a pH of 4.76, not be a suitable buffer for most practical applications? [Hint: concentration] What would you have to do to correct this deficiency, i.e. how would you make a useful buffer at the same pH? 2
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E1-3 Membrane lipids serve not only structural roles, but can also mediate cell recognition. Sketch the approximate general structure of the molecule associated with the red blood cell membrane that determines blood type. What kind of lipid is this, and why is it not considered a triglyceride, even though its overall structure is quite similar to one? How can the four blood types A, B, AB, and O be accounted for genetically?
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This note was uploaded on 04/17/2008 for the course BIO 101 taught by Professor Sia during the Spring '08 term at Rochester.

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Cumulative Exam Questions - E1-1 Without using a...

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