BIS102 MT1 W09 Key Hilt

BIS102 MT1 W09 Key Hilt - 1 NAME: _ . Last, First...

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1 NAME: ____________________________ . Last, First BIOLOGICAL SCIENCES 102, Section 1, Winter Quarter MIDTERM EXAMINATION I January 26, 2010 Winter Quarter Dr. Marilynn Etzler and Dr. Ken Hilt Check the Appropriate Categories Below: Undergraduate ________ Graduate __________ Concurrent __________ INSTRUCTIONS: WRITE YOUR NAME AT THE TOP OF EACH PAGE There are eight pages to this examination. Please count them before you start to make sure they are all present. Place your answer in the space provided beneath the question. Do not use any other paper; if you need more room, use the back of these sheets, but clearly state that you are continuing your answer on the back. PAGE VALUE SCORE 3 13 4 17 5 27 6 15 7 18 8 10 TOTAL 100 log 1.0 = 0.00 log 1.5 = 0.18 log 2.0 = 0.30 log 2.5 = 0.40 log 3.0 = 0.48 log 3.5 = 0.54 log 4.0 = 0.60 log 4.5 = 0.65 log 5.0 = 0.70 log 6.0 = 0.78 log 7.0 = 0.84 log 8.0 = 0.90 log 9.0 = 0.95
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2 Name: ________________ pKa Values of Some Amino Acids Amino acid α -COOH α -NH 3 + R Group Alanine 2.3 9.6 --- Arginine 2.2 9.0 12.5 Asparagine 2.0 8.8 --- Aspartic acid 2.1 9.8 3.9 Cysteine 1.7 10.8 8.3 Glutamine 2.2 9.1 --- Glycine 2.1 9.4 --- Histidine 1.8 9.2 6.0 Isoleucine 2.4 9.7 --- Leucine 2.4 9.6 --- Lysine 2.2 9.0 10.4 Methionine 2.3 9.2 --- Phenylalanine 1.8 9.1 --- Serine 2.2 9.2 --- Tyrosine 2.2 9.1 10.1
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3 Name: ________________ 1. An enzyme-catalyzed reaction was carried out in a solution containing 0.3 M Tris buffer. The pK a of Tris is 8.1. The pH of the reaction mixture at the start was 8.4. As a result of the reaction, 0.05 mole/liter of H + was produced. Please answer the following questions: (A simplified log table is provided on the cover page of this exam.) a) (3 points) What was the ratio of Tris (free base) to Tris + Cl - at the start of the reaction? Note: This problem is almost identical to Problem 41 of the Segel book, which was assigned to you in assignment 2. The solution to this problem was posted on the web site. Base:Acid = 2:1 b) (4 points) What was the final pH of the reaction mixture? pH = 8.1 c) (3 points) Over what pH range can Tris be used as an effective buffer? Between pH 7.1 and 9.1 d) (3 points) Briefly state how one could alter the above Tris buffer so that the pH would not change as much as you found in part (b) above. (Note: the pH at the beginning of the reaction must be 8.4.)
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This note was uploaded on 10/22/2010 for the course BIS 102 taught by Professor Hilt during the Fall '08 term at UC Davis.

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BIS102 MT1 W09 Key Hilt - 1 NAME: _ . Last, First...

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