Dental Biochemistry EXAM I

Transcription

1 Dental Biochemistry EXAM I August 29, 2005 In the reaction below: CH 3 -CH 2 OH -~ ethanol CH 3 -CHO acetaldehyde A. acetoacetate is being produced B. ethanol is being oxidized to acetaldehyde C. acetaldehyde is being oxidized D. ethanol is being reduced 2. A single nitrogen atom may exist in isolation. A. True B. False 3. A hydrophobe is best exemplified by A. polyphosphate compounds B. a molecule such as methanol C. a saturated hydrocarbon D. the amino acid arginine 4. The role of phosphorus in biological systems involves A. development and maintenance of the skeletal system B, energy utilization C. buffering capacity D. all of the above I

2 5. A reaction is exergonic when A. energy is required to make the reaction proceed B. it causes an entropy decrease in the system C. an increase in enthalpy is attained D. the free energy of the system decreases 6. If you know the standard free energy yield of a reaction, you may calculate A. the number of intermediates encountered between reactants and products B. the rate of the reaction C. the free energy yield for the reaction at any concentration of reactants and products D. the equilibrium constant for the reaction 7. In the case of coupled biochemical reactions, the free energy output of the combined reactions is A. the sum of the equilibrium constants of the individual reactions B. impossible to determine C. the sum of the free energy yields for the individual reactions D. equal to that of the more favorable reaction 8. If the hydrochloride salt of the amino acid histidine is titrated with a strong base, there will be multiple zones of buffering. How many? A. 1 B. 2 D. 4 F. 5 7

3 9. Following the addition of one equivalent of base to the hydrochloride salt of isoleucine, the overall charge on the amino acid will be A. 0 B. -1 C. +1 D. +2 F A buffer system is described by all but one of the following statements. Choose the incorrect statement. A. a buffer system is composed of an acid and its conjugate base B. A buffer system is most effective in the ph domain near the pk of its conjugate acid. C. a buffer system requires a strong acid which completely dissociates in aqueous solutions. D. a buffer system must have components in sufficient quantity to compensate for expected levels of agents which may change ph. F. the bicarbonate buffer system facilitates ph regulation of the circulation. 11. All living creatures, with the exception of some bacteria, utilize L- amino acids in the synthesis of proteins since this A. enhances the function of proteins with respect to specificity B. allows for efficient formation of secondary structure C. enables the proteins to bind small ions D. allows the formation of ribosome-mrna complexes 12. The only amino acid which has an achiral a-carbon is A. A B. P C. G D. C F. D

4 13. The diversity of amino acids resides in A. their ability to form polymers of indeterminate length B. the side chains (R-groups) C. the reactivity of a-carbon atoms D. the reactivity of carboxyl groups 14. The developer of the process to capture atmospheric N 2 as NH 3 (ammonia) was A. Aristotle B. F.J. Miller C. J.P. Sartre D. F. Haber F. L. Meitner 15. The following are characteristics of a peptide bond except A. the C-N bond is shorter than an ordinary C-N bond B. it maintains six atoms in a planar configuration C. the cis conformation is energetically more favorable than trans D. it has characteristics of a resonance system 16. Fxamples of 2 structure of proteins include all of the following except A. alpha helix B. beta pleated sheet C. polyproline helix D. four helix bundle F. ~3-turn 17. The allosteric hemoglobin molecule represents an example of protein A. primary structure B. secondary structure C. tertiary structure D. quaternary structure 4

5 18. Photosynthesis involves A. the oxidation of water and reduction of carbon dioxide B. the formation of carbonated water C. the reduction of water and oxidation of carbon dioxide D. all of the above 19. The buffering capacity of a protein may be ascribed to its content of A. proline B. arginine C. serine D. histidine F. aspartic acid 20. The sequence: Lys - Lys - Lys - Lys - Lys would, at neutral ph A. be required for a polyproline helix B. would stabilize an a-helix C. would frequently be found in a f3-turn D. would destabilize an a-helix 21. For the hexapeptide: Gly - Asp - Pro Gly - Ser - Glu, the net charge at ph 7.0 would be A. 0 B. +1 C. +2 D. -1 F The element which bestows the basic structural properties on biological molecules is A. H B. C C. N ft 0 F. K

6 23. The isoelectric point of a monoamino, monocarboxylic amino acid can be calculated as A. the ph at which the amino acid precipitates from solution B. a function of the molecular mass of the amino acid C. the average of the PKa S of the amino and carboxyl groups D. as the PKa of the carboxyl group 24. Hydrophobic bonds are A. formed between highly polar molecules B. more difficult to disrupt than covalent bonds C. regarded as high energy bonds D. play an extensive role in the formation of cell membranes 25. The number of amino acids in one turn of a peptide chain in ~- pleated sheet conformation is A. more than that in one turn of an a-helix B. less than that in one turn of an a-helix C. about the same as that in one turn of an a-helix D An amino acid likely to serve as a site for protein glycosylation is A. serine B. proline C. alanine D. methionine F. leucine 27.An amino acid which serves as a precursor for the psychoactive agent, serotonin, is A. valine B. glycine C. tryptophan D. arginine F. aspartic acid 6

7 28. Of the amino acids noted in questions #26 and 27, which is the most basic (the one with the highest isoelectric point)? A. aspartic acid B. arginine C. serine D. leucine E. methionine 29. The primary structure of a protein may be determined by A. molecular sieve chromatography B. ultracentrifugation C. Edman degradation D. ion-exchange chromatography E. reversed-phase chromatography 30. If one knows the concentration of an organic acid and the extent to which it is ionized (dissociated), can the ph of the solution be calculated? A. Yes B.No 31. For a chemical reaction to be spontaneous and liberate free energy A. the change in enthalpy must be negative (-Al-I) B. the change in entropy must be negative (-AS) C. the observed values of AH and AS must calculate to a negative AG (- AG) D. the change in entropy must be positive (+AS) E. the change in enthalpy must be positive (+AH) 32. The major thermodynamic factor in the melting of ice at room temperature is the entropic factor favoring liquid water over crystalline ice. A. True B. False 33. The molecular weight of a protein may be determined by A. SDS-PAGE electrophoresis B. Ion-exchange chromatography C. Dialysis D. Denaturation using a chaotropic agent F. All of the above 7