V, S A hydrogen donor for a hydrogen bond
Y, U A hydrogen acceptor for a hydrogen bond
U, V Could have an ionic interaction
X, R, T Could have a hydrophobic interaction
Quiz 1 Key |
|
1-4. Use the letters labeling different parts of the molecule. Use a letter only once .
|
V, S A hydrogen donor for a hydrogen bond |
Y, U A hydrogen acceptor for a hydrogen bond |
|
U, V Could have an ionic interaction |
|
X, R, T Could have a hydrophobic interaction |
Note about grading 1-4: The most common mistake was choosing a ring N for "Could have an ionic interaction". Actually, this is just asking which groups are charged and could interact with another charged group.
5-7. Use these reactions and the values for ΔG°′. All reactions are shown as irreversible.
Reaction |
ΔG°′ (kJ/mol) |
What is ΔG°′ for converting P to R? – 17.6 kJ/mol |
|
A. O → P |
– 32.2 |
Which reaction is most favorable? D |
|
B. P → Q |
+ 13.3 |
Which reaction is least favorable? H |
|
C. Q → R |
– 20.9 |
Which reaction has the largest Keq? D |
|
D. R → S |
– 33.5 |
Which reaction has Keq = 1? F |
|
E. S → T |
– 2.9 |
Which reaction has the smallest Keq? H |
|
F. T → U |
0 |
What is ΔG°′ for converting Q to S? – 54.4 kJ/mol |
|
G. U → V |
– 3.8 |
What is ΔG°′ for converting R to T? – 36.4 kJ/mol |
|
H. V → W |
+ 29.7 |
What is ΔG°′ for converting V to T? + 3.8 kJ/mol |
|
Notes about 5-7: Each quiz had only four reactions, always labeled A-D, always a sequence out of these (citric acid cycle) reactions. For those reasons, answers in this key may not match the answers for the original quiz.
8-10. Draw a water molecule with a hydrogen bond to this molecule:
Diagrams here show only one possibility. There are other correct answers.
This is how I graded 8-10: 1 point for drawing a water molecule, 1 point for choosing the correct part of the molecule (must be able to form a hydrogen bond), 0.5 point for showing the hydrogen bond correctly (not as a solid line, which indicates a strong, covalent bond), and 0.5 point for having the correct orientation in the hydrogen bond.
A few people added a charge to the molecule and lost 0.5 point for doing so. Although charged groups can form hydrogen bonds, the charge isn't required, and it actually isn't appropriate to add one.