practicequizchap1-3-09-answers

practicequizchap1-3-09-answers - Name:_ ID #:_...

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Name:_______________________________ ID #:________________________________ BCMB/BIOL/CHEM 3100; Practice Quiz, Chapters 1-3; August 28, 2009 Answer all questions to the best of your ability. Be concise. 1. The phosphate buffer system is important for buffering intracellular pH. If the total cellular concentration of phosphate is 20 mM, and the pH is 7.4, what is the concentration of the predominant phosphate species HPO 4 2- and H 2 PO 4 - ? [Hint: the pKa of H 2 PO 4 - HPO 4 2- is 7.2] (9 points) ------- Answer pH = pKa + log [A-] / [HA] (1.5 point) 7.4 = 7.2 + log [A-] / [HA] (1.5 points) 0.2 = log [A-] / [HA] (2 points) 1.58 = [A-] / [HA] (2 point) Therefore, the amount of A- = 1.58 / 1 + 1.58 = 61.2% 61.2% of 20 mM = 12.25 mM [A-] = HPO 4 2- (1 points) 38.8% of 20 mM = 7.75 mM [HA] = H 2 PO 4 - (1 points) 2. List the four types of noncovalent interactions that are responsible for the interactions within and between macromolecules in living organisms. List them in the order of the
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This note was uploaded on 12/03/2011 for the course CHEM 3100 taught by Professor Dervartanian during the Fall '09 term at UGA.

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practicequizchap1-3-09-answers - Name:_ ID #:_...

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