MIT Biology Department 7.012: Introductory Biology - Fall 2004 Instructors: Professor Eric Lander, Professor Robert A. Weinberg, Dr. Claudette Gardel
7.012 Practice Quiz 1
Actual Quiz 1 (closed book) will be given Monday10/4 at 10:00 am
No Sections on Monday or Tuesday 10/4-10/5 (No Kidding.)
Quiz Review Session
Thursday, 9/30
Tutoring Session
7:00 - 9:00 pm 4:00 - 6:00 pm
Friday, 10/1
Question 1
Shown below are the structures of three amino acids. NH 3 H C CH2 O C O Phenylalanine (Phe) OH H C CH CH3 C O O Threonine (Thr) NH 3 NH 3 H C CH2 O C O Tyrosine (Tyr) OH
Using the blanks below, rank these three in order of the hydrophobicity of their side chains. a) b) c) Most Hydrophobic Intermediate Least Hydrophobic
d) Explain why (a) is more hydrophobic than (b).
e) Explain why (b) is more hydrophobic than (c).
Question 2
Shown below is a close up of a substrate (UDP-Glucose) bound to the active site of an enzyme (UTase). The shaded area is the enzyme; the structure of the substrate is shown.
CH2 OH H OH H OH O H OH H H O
Ser161 H O CH2 H H Arg 31 OH H O
NH 2 N N H H OH O
O P O P O O O
Two amino acids of the enzyme are highlighted: Arg 31 and Ser 161. 2
Question 2, continued
a) Part (I) of the figure below shows the relative positions of Arg 31 and the portion of the substrate with which it interacts; part (II) shows the structure of arginine. (I) O O NH H C CH2 O C CH2 (II) H CH2 N C NH 2
O P O P O O O Arg 31
Arginine
NH 2
The side chain of Arg 31 interacts with the portion of the substrate shown previously. What type of interaction(s) is/are possible between the side chain of Arg 31 and this portion of the substrate (circle all that apply) hydrophobic interaction Hydrogen bond ionic bond van der Waals interaction
b) Part (I) of the figure below shows the relative positions of Ser 161 and the portion of the substrate with which it interacts; part (II) shows the structure of serine. (I) Ser161 NH O O H C CH2 O C OH O P O P O O O Serine

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