| Chemistry and Environmental Studies 247 | Exam 01 | Winter 2008–09 |
Respond, primarily on the basis of Chapters 1 to 4, to any six (6) of the following on a take-home and open (non-human) resources rubric. Although you do not need to write extensively, please annotate your work clearly enough to make plain all of your intentions and thinking.
| 1. | Calcium hydroxide is moderately soluble in aqueous media, but the precipitation of very insoluble calcium compounds is a possibility from biological fluids. Consider the permitted free Ca2+ ion concentration at 37 oC in a biological compartment where we will assume the pH to be 7.4 and the HPO42– concentration to be 1.0 mM (1.0 x 10–3 mol L–1). | ||||||
| a. | At that temperature, Kw = 2.3 x 10–14. Calculate the concentrations of H+ and OH– ions. | ||||||
| b. | At that temperature, K3 = 5.7 x 10–13 for phosphoric acid. Calculate the concentration of PO43– ions. | ||||||
| c. | At that temperature, Ksp = 7.9 x 10–34 for simple calcium phosphate, Ca3(PO4)2. How big can [Ca2+] become without risk of precipitating that compound? | ||||||
| d. | At that temperature, Ksp = 2.03 x 10–59 for hydroxyapatite, Ca5(PO4)3(OH), a major constituent of bone and tooth structures. How big can [Ca2+] become without risk of precipitating that compound? | ||||||
| e. | Find support in the text for the order of magnitude of free calcium concentration found in (c), (d), and similar calculations. | ||||||
| 2. | Although the first-row transition elements exist in the sea at thousand-fold lower abundance than any of the bulk biological elements, nevertheless all life forms do require one or more of the transition elements. Offer reasons why (based on atomic and chemical properties), touching also upon some of the strategies for uptake and retention. | ||||||
| 3. | Although the elements Al and Ti exist in the earth’s crust at higher abundance than S and P, the latter ubiquitously occur in biological organisms while the former do not. Offer reasons why (based on atomic and chemical properties). | ||||||
| 4. | Explain what is meant by water exchange rates for metal ions. Then briefly discuss the relevance of such rates to the biological roles of selected metal ions. | ||||||
| 5. | Why is it functionally important for many proteins to be situated in membranes? | ||||||
| 6. | What do compartments do for biological systems? | ||||||
| 7. | What does tubulin do for a cell? | ||||||
| 8. | “Na+ and K+ are biologically totally distinct and are not similar ions as in chemistry.” Amplify, illustrate, and comment. | ||||||
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