Quiz 2, BICH 410 (MWF 3-3:50P), Friday October 8, 1999
Write your name on each page. Clearly circle your response to multiple-choice questions. No partial credit for multiple-choice questions
gas constant R 8.315 J/mol-K
1. (3 pts) Which amino acid sidechain from the choices below would be the worst nucleophile in an enzyme active site?
Answer: B (see Fig. 11-10)
- A) serine
- B) alanine
- C) histidine
- D) cysteine
- E) lysine
2. (3 pts) Why does fetal hemoglobin bind oxygen with a higher affinity than adult hemoglobin?
- A) The heme group is different in fetal hemoglobin.
- B) The Hill coefficient is larger for fetal hemoglobin.
- C) Carbon monoxide does not compete with oxygen for binding to fetal hemoglobin.
- D) Fetal hemoglobin has a lower affinity for BPG.
- E) All of the above are true.
3. (3 pts) Which nucleotide base from the choices below cannot exist in keto vs. enol tautomeric forms?
Answer: A; adenine is only base that lacks a keto group
- A) adenine
- B) cytosine
- C) guanine
- D) thymine
- E) uracil
4. (3 pts) Three essential amino acid residues in the active site of chymotrypsin form a catalytic triad. Which of the following is a role for these residues in catalysis?
- A) The histidine residue forms a covalent intermediate during the reaction.
- B) The aspartate residue orients the substrate properly for the reaction.
- C) The serine residue acts as an electrophile during the reaction.
- D) The histidine residue facilitates the reaction by acting as an acid-base catalyst.
- E) The aspartate residue forms part of the specificity pocket of the enzyme active site.
5) (2 pts) Which of the following compounds is not a nucleotide?
- A) 2,3-bisphosphoglycerate
- B) Coenzyme A
- C) AMP
- D) NAD+
- E) FAD
6) (3 pts) Consider the reaction profile (transition state diagram) shown below. Select the answer that correctly identifies the values 1, 2, and 3 depicted on this graph.
(graph is modified from Fig. 11-5 in book)
- A) 1: deltaG 2: deltaGact(cat) 3: deltaGact(uncat)
- B) 1: deltadeltaGact 2: deltaG 3: deltaGact(uncat)
- C) 1: deltaG 2: deltaGact(uncat) 3: deltadeltaGact
- D) 1: deltaGact(uncat) 2: deltaG 3: deltaGact(cat)
- E) 1: deltaG 2: deltadeltaGact 3: deltaGact(cat)
7) (3 pts) Consider the two oxygen binding curves for hemoglobin labeled A and B. Which statement(s) is/are true?
(graph consists of two sigmoid curves - curve A on left, curve B on right)
- A) A lower pH shifts curve A to B.
- B) A higher CO2 concentration shifts curve A to B.
- C) Addition of BPG shifts curve A to B.
- D) All of the above are true.
- E) None of the above are true.