6. Tryptophan is a precursor for the neurotransmitter(s)
(A)serotonin
(B) norepinephrine
(C) adenine
(D) all of the above
(E) none of the above

2. Which is not correct concerning the models that are accepted to describe cooperative binding? (A) In the sequential model, the binding of a ligand changes the conformation of the subunit to which it binds, which in turn induces a change in neighboring subunits. (B) All known allosteric proteins exhibit either the concerted or sequential model exclusive of the other. (C) Both models incorporate a low affinity T-state and a higher affinity R-state. (D) Both models explain the sigmoid-shaped binding curve. (E) In the concerted model, all molecules exist either in the T-state or the R-state.

3. What two properties of water are important for biological interactions? (A) the polarity of water (B) the density of water (C) the cohesive properties of water (D) A and C (E) B and C

4. Excess alcohol consumption can lead to Wernicke-Korsaff syndrome due to the lack of the vitamin thiamine. Which of the following metabolic conversions cannot occur in the absence of thiamine? (A) Pyruvate + CO2 → oxaloacetate (B) Pyruvate → acetyl-CoA + CO2 (C) a-ketoglutarate → succinyl-CoA + CO2 (D) Phosphoenolpyruvate + CO2 → oxaloacetate (E) B and C

5. The ultimate reductant in synthesis of deoxyribonucleotides is: (A)FADH2 (B) NADH (C) NADPH (D) quinine (E) none of the above

7. The carbon skeletons for amino acids are intermediates found in (A) glycolysis (B) citric acid cycle (C) pentose phosphate pathway (D) all of the above (E) none of the above.

8. Ketogenic amino acids are degraded to which of the following metabolites? (A) pyruvate (B) acetyl-CoA (C) acetoacetate (D) all of the above (E) B and C

9. Two-dimensional electrophoresis is a combination of what two techniques? (A)isoelectric focusing and affinity chromatography (B) ion-exchange chromatography and SDS-PAGE (C) affinity chromatography and SDS-PAGE (D) isoelectric focusing and SDS-PAGE (E) isoelectric focusing and ion-exchange chromatography

10. The use of synthetic peptides includes (A)use as antigens for making antibodies (B) drugs (C) "hooks" used in purification (D) all of the above (E) A and C

11. Which of the following describes the Bohr effect? (A) Lowering the pH results in the release of O2 from oxyhemoglobin. (B) Increasing the pressure of CO2 results in the release of O2 from oxyhemoglobin. (C) Increasing the pH increases the T-form of hemoglobin. (D) All of the above. (E) A and B.

12. Which of the following is not correct concerning the oxygenation plot of proteins X and Y shown below? (A) Protein X exhibits tighter oxygen binding than protein Y. (B) Protein Y would function as a better transport protein than protein X. (C) Protein X exhibits cooperative binding, whereas Y does not. (D) Protein X corresponds to myoglobin, and protein Y corresponds to hemoglobin. (E) Protein Y contains multiple binding sites.