mtK - Net ID KEY BIOMG 3310 MIDTERM EXAM 10/21/10 1. 2. 3....

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Net ID KEY BIOMG 3310 MIDTERM EXAM 10/21/10 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. TOTAL BE SURE TO WRITE/PRINT LEGIBLY . IF WE CAN'T READ IT, WE CAN'T GRADE IT! (SERIOUSLY) PRINT NAME (LAST, FIRST) ON THE BACK TOP OF THE LAST PAGE AND ONLY THE LAST PAGE Use these pK a values unless others are given in a problem: terminal COOH 4 terminal NH 3 + 9 R-GROUPS: Asp 4 Glu 4 Cys 8 Tyr 10 His 7 Lys 10 Arg 12
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1. (7 pts) Given that the side chain of Ala is -CH 3 . a . On the right, draw Ala at pH 7. Show every atom. Use symbols α and β to label those carbons. b . Below, draw Ala-Ala at pH 7. Circle the 6 atoms that line in a plane. Show every atom. (No need for α and β here). 2. (10 pts) Hb has a terminal amino and a terminal carboxyl that can form an ion pair. a. What fraction of these ionizable groups are actually in an ion pair: AT BOTH pH VALUES, THE CARBOXYL IS MORE THAN 99.9% NEGATIVELY CHARGED, SO CONSIDER ONLY THE AMINO: _ ~0.97 _ at pH 7.5 pH = pKa + log[un]/[prot], so 7.5 = 9.0 + log[NH2]/[NH3+], -1.5 = log[NH2]/[NH3+], 0.03 = [NH2]/[NH3+] _ ~0.99 _ at pH 7.0 pH = pKa + log[un]/[prot], so 7.0 = 9.0 + log[NH2]/[NH3+], -2.0 = log[NH2]/[NH3+], 0.01 = [NH2]/[NH3+] b. Draw curves of θ vs pO 2 that correspond to pH values in question 2a. Label curves and axes, and show at least two numerical values on each axis. θ c. Which curve(s) in 2b involve BPG that stays bound to the Hb at all the values of pO 2 shown on your graph? Circle answer: pH 7.5 pH 7.0 both curves neither curve 3. (2 pts) Circle each pair below that are isozymes: Hb/Mb hexose/hexokinase muscle hexokinase/brain hexokinase tyrosine kinase/serine kinase 4. (5 pts) We know that O 2 binds to the heme Fe ++ of Mb. Then why is the polypeptide needed?! a. Briefly (BRIEFLY) describe two important properties of the Mb polypeptide : i. GOOD FIT TO HEME ii. GOOD FIT TO O 2 iii. STABLE STRUCTURE b. We can refer to the Mb polypeptide as “apomyoglobin”. What term refers to just the heme group: PROSTHETIC GROUP 1.0 0.5 0.0 pO2, TORR 0 50 100 7.5 7.0
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5. (6 pts) 6 categories of forces are important for stabilizing protein structure. Name each one, and state whether the geometry of the interaction is highly directional,
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mtK - Net ID KEY BIOMG 3310 MIDTERM EXAM 10/21/10 1. 2. 3....

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