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BCH 4053 June 2, 2000 (10) 1. HOUR TEST 1 NAME_____________________ Carbonic Acid in solution is an equilibrium mixture of H2 CO3 and dissolved CO2 . If its standard state is taken a 1 M for the sum of both forms, then pK1 for the following reaction is 6.1: H2 CO3 (total) € H+ + HCO3 - (a) Calculate the [HCO3 -]/[H2 CO3 (total)] ratio in blood at pH 7.4. Page Points 1 2 3 4 ____ ____ ____ ____ Total ______ (b) Normally buffers have their best buffering capacity at their pK. Yet bicarbonate buffer is a very good buffer at pH 7.4, even better than at its pK of 6.1. Explain why. 2. (10) Draw the structure of the following peptide, showing all dissociable functional groups in their fully protonated form, and indicate the approximate pK of each of the dissociable functional groups: (a) Lys.Cys.Arg.Tyr.Glu (1) (b) What is the charge on the fully protonated form of the peptide? (1) (c) What is the charge on the fully unprotonated form of the peptide? (1) (d) What is the approximate pI of the peptide? (1) (e) What is the net charge on the peptide at pH 6.0? BCH 4053 --Hour Test 1 Page 2 Name________________________ (12) 3. Formic acid has a pK of 3.75. How many mL of 0.1 M NaOH must be added to 100 mL of 0.05 M formic acid to make a buffer solution with a pH of 4.25? (20) 4. Identify the following amino acids by giving the name, the three letter abbreviation, and the one letter abbreviation. The number of amino acids in each category is given in parenthesis. Category Contains a sulfur atom (2) Name Abbreviations _______________________________________________________ _______________________________________________________ Absorbs UV light above 250 nm (3) _______________________________________________________ _______________________________________________________ _______________________________________________________ Contains an amide group in the side chain (2) _______________________________________________________ _______________________________________________________ Contains an imidazole group in the side chain (1) _______________________________________________________ Contains a guanidinium group in the side chain (1) _______________________________________________________ An alpha imino acid (1) _______________________________________________________ BCH 4053 --Hour Test 1 5. Page 3 Name________________________ The standard free energy change for ATP hydrolysis is –30.5 kJ/mol and for glycerol-3phosphate hydrolysis is –9.2 kJ/mol. (a) Calculate ∆Go ' for the glycerokinase reaction: (4) ATP + glycerol € ADP + glycerol-3-phosphate (4) (b) Calculate ∆G for the reaction if [glycerol-3-P] = 10 mM, [glycerol] = 0.10 mM, [ATP] = 5.0 mM, and [ADP] = 1.0 mM. (Temperature = 37 o C; R = 8.314 J/mol-K) (4) (c) Calculate Keq' for this reaction at 37 o C. (5) 6. List five unusual properties of water resulting from its hydrogen bonded structure. (5) 7. Draw a diagram to show how water will interact with an amphipathic molecule such as sodium palmitate. What is the name for the structure assumed by the sodium palmitate in water? BCH 4053 --Hour Test 1 For Questions 8 to 14, put a check mark by the best answer. (14 points) 8. Of the following weak chemical interactions, which is the weakest? ____ hydrogen bonding ____ hydrophobic bonding ____ induced dipole-induced dipole attraction ____ dipole-dipole attraction ____ coulombic attraction 9. Hydrophobic bonding between non-polar groups is primarily a result of: ____ dispersion forces of attraction between the groups. ____ electrostatic attraction between the groups. ____ an entropy increase in water when the groups associate. ____ an entropy decrease in water when the groups associate. 10. Which of the following compounds has the highest ∆Go ' of hydrolysis? ____ ATP ____ Pyrophosphate ____ glucose-1-phosphate ____ phosphoenolpyruvate 11. A closed system ____ exchanges matter and heat with surroundings. ____ exchanges only heat with surroundings. ____ exchanges heat and work with surroundings. ____ exchanges nothing with surroundings. 12. A process with a negative entropy change and a positive enthalpy change will be ____ spontaneous at all temperatures. ____ non-spontaneous at all temperatures. ____ spontaneous at high temperatures only. ____ spontaneous at low temperatures only. 13. Which amino acids have two chiral carbons? ____ lysine and arginine ____ threonine and glutamine ____ leucine and isoleucine ____ threonine and isoleucine ____ proline and methionine Page 4 Name________________________ 14. A cation exchange column ____ has a positively charged functional group and binds cations. ____ has a negatively charged functional group and binds anions. ____ has a positively charged functional group and binds anions. ____ has a negatively charged functional group and binds cations. For Questions 15 and 16, put a check by all correct answers (8 points) 15. Peptide A has a pI of 5.5. Peptide B has a pI of 8.5. Which of the following is true? ____ Both peptides will bind to an anion exchange resin at pH 7. ____ Both peptides will bind to a cation exchange resin at pH 7. ____ Peptide A will bind to a cation exchange resin at pH 7. ____ Peptide B will bind to a cation exchange resin at pH 7. ____ Peptide A will bind to an anion exchange resin at pH 7. ____ Peptide B will bind to an anion exchange resin at pH 7. ____ Both peptides will bind to an anion exchange resin at pH 4. ____ Both peptides will bind to a cation exchange resin at pH 4. 16. With respect to proteins, which of the following statements are true? ____ Proteins are polymers of sugar residues. ____ Amino acids are building blocks of proteins. ____ Peptide bonds are amide bonds. ____ The primary structure refers to the overall three dimensional structure of the protein. ____ The secondary structure refers to the ordered repeating structure along the peptide backbone. ____ The quaternary structure refers to the orientation around the peptide bond. ____ The alpha helix is an example of secondary structure. ____ Globular proteins fold up so that the nonpolar amino acid side chains are on the interior.