EXAM98_5 - NAME _ I. _/245 II. _/ 50 III. _/ 32 IV. FINAL...

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NAME ________________________________ FINAL EXAM I. __________________/245 December 19, 1998 Biochemistry I II. __________________/ 50 BI/CH421, BI601, BI/CH621 III. __________________/ 32 IV. __________________/ 73 TOTAL /400 I. MULTIPLE CHOICE (245 points) Choose the BEST answer to the question by circling the appropriate letter. Questions 1-17 are worth 10 points each (170 pts.) and questions 18-32 are worth 5 points each (75 pts.). 1. An enzyme reaction to be studied at pH 4.0 can best be carried out using a buffer solution made from which of the following acids, and their conjugate bases, with K a values as shown? (Assume that there is no direct interaction between the buffer molecule and the enzyme to be studied.) Acid K a A. Phosphoric acid 7.3 x 10 -3 B. Lactic acid 1.4 x 10 -4 C. Acetic acid 1.2 x 10 -5 D. Dihydrogen phosphate ion (H 2 PO 4 - ) 6.3 x 10 -8 E. Bicarbonate ion (HCO 3 - ) 6.3 x 10 -11 2. In the diagram below, the plane drawn behind the peptide bond indicates the: H C a C N H R O a C A. plane of rotation around the C a -N bond. B. absence of rotation around the C-N bond because of its partial double bond character. C. region of steric hindrance determined by the large C=O group. D. theoretical space between -180 and +180 that can be occupied by the j and f angles in the peptide bond. E. region of the peptide bond that contributes to a Ramachandran plot. Page 1
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NAME ________________________________ 3. Which of the following amino acids is the most soluble in water at pH 7.0? A. Glutamate B. Tryptophan C. Leucine D. Tyrosine E. Phenylalanine 4. The folded states of globular proteins in aqueous solutions are stabilized primarily by ______. A. hydrophobic interactions B. peptide bonds C. phosphodiester bonds D. ionic bonds E. disulfide bonds 5. Which of these statements about enzyme-catalyzed reactions that obey Michaelis-Menten kinetics is false ? A. At saturating levels of substrate, the rate of an enzyme-catalyzed reaction is proportional to the enzyme concentration. B. The Michaelis-Menten constant K m equals the [S] at which V = 1/2 V max . C. If enough substrate is added, the normal V max of a reaction can be attained even in the presence of a competitive inhibitor. D. The rate of a reaction decreases steadily with time as substrate is depleted. E. The activation energy for the catalyzed reaction is the same as for the uncatalyzed reaction, but the equilibrium constant is more favorable in the enzyme-catalyzed reaction. 6. The most efficient substrate of an enzyme is usually considered to be the substrate with the ________. A. largest k cat B. largest K m C. largest k cat / K m D. smallest k cat / K m E. smallest K m 7. Certain restriction enzymes produce cohesive (sticky) ends. This means that they: A. cut in regions of high GC content, leaving ends that can form more hydrogen bonds than ends of high AT content. B.
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This note was uploaded on 10/17/2011 for the course CHEM 653 taught by Professor Wei, robert during the Spring '11 term at Cleveland State.

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EXAM98_5 - NAME _ I. _/245 II. _/ 50 III. _/ 32 IV. FINAL...

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