2. Eric uses a computer software to simulate a 20-residue peptide in different structures. Structure A is an α-helix structure; structure B is a β-strand; structure C is a helix in the collagen structure. The length of these structures should be: (A)C＞B＞A (B) C＞A＞B (C) B＞A＞C (D) A＞B＞C (E) B＞C＞A

5. Both water and glucose share an–OH that can serve as a substrate for a reaction with the terminal phosphate of ATP catalyzed by hexokinase. Glucose, however, is about a million times more reactive as a substrate than water. The best explanation is that: (A) the larger glucose binds better to the enzyme; it induces a conformational change in hexokinase that brings active-site amino acids into position for catalysis. (B) glucose has more –OH groups per molecule than does water. (C) the–OH group of water is attached to an inhibitory H atom, while the glucose –OH group is attached to C. (D) water and the second substrate, ATP, compete for the active site resulting in a competitive inhibition of the enzyme. (E) water normally will not reach the active site because it is hydrophobic.

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