Assessment Exam: Biochemistry_Chem

First Name:
Last Name:
Social Security Number:

1. A kinase is an enzyme that
   A. breaks a bond by inserting the elements of water
   B. transfers a phosphoryl group from ATP
   C. removes a water molecule
   D. transfers a phosphoryl group to a different position on a molecule
   E. hydrolyzes phosphate esters
   


2. Which of these contains a thioester bond?
   A. a-ketoglutarate
   B. cystine
   C. N-acetylglucosamine
   D. ATP
   E. succinylCoA
   


3. Which amino acid side chain would not be expected to participate in "covalent" enzyme catalysis?
   A. lys
   B. cys
   C. ser
   D. leu
   E. his
   


4. Four tripeptide mixtures (I-IV) are separated at pH 6.0 using one-dimensional high voltage paper electrophoresis.
   I pro-asp-thr
   II lys-ala-val
   III tyr-gly-his
   IV glu-phe-arg
   
   The predicted order of separation of the peptides, listing first the peptide migrating closets to the cathode (negative electrode) and last the peptide migrating closest to the anode, is
   
   A. III, II, I, IV
   B. II, III, IV, I
   C. III, IV, I, II
   D. I, III, II, IV
   E. II, IV, I, III
   


5. In a yeast cell growing aerobically on glucose, which would provide most of the energy for growth?
   A. glycolysis to ethanol and CO₂
   B. the nitrogenase reaction
   C. gluconeogenesis
   D. glycolysis to TCA cycle and oxidative phosphorylation
   E. glycolysis to lactate
   


6. The analysis of proteins by SDS-PAGE
   A. uses dithiothreitol to oxidize cysteine to cystine
   B. involves protein-detergent complexes that differ in charge-to-mass ratio, but not in mass
   C. involves the disruption of the quaternary structure, but not in tertiary structure
   D. achieves separation on the basis of the isoelectric points of the proteins
   E. yields the subunit molecular weight for an oligomeric protein
   


7. Gel filtration chromatography separates on the basis of
   A. surface charged (+/-) groups
   B. size and charge
   C. affinity for specific substrates
   D. affinity for hydrophobic compounds
   E. vapor pressure
   


8. During glycolysis, which of the following participates in a substrate-level phosphorylation reaction?
   A. glucose-6-phosphate
   B. 2-phosphoglycerate
   C. 1,3-bisphosphoglycerate
   D. glyceraldehyde-3-phosphate
   E. fructose-1,6-bisphosphate
   


9. Double-stranded DNA was found to have 20%G. What is the content of A?
   A. 20%
   B. 30%
   C. 50%
   D. 80%
   E. insufficient information given
   


10. The oxidation of 1 mmol of glucose in glycolysis, under aerobic conditions yields a net of
    A. 2mmol lactate and 2mmol ATP
    B. 2mmol ethanol, 2mmol of NADH and 2mmol of ADP
    C. 2mmol pyruvate, 2mmol of NADH and 2 mmol of ATP
    D. 2mmol of lactate, 2mmol of NADH and 6mmol of ATP
    E. 2mmol of pyruvate and 2mmol of ATP
    


11. What can you conclude about the thermodynamic spontaneity of a reaction that has a negative value for DH and a positive value for DS?
    A. the reaction is not spontaneous under any conditions
    B. the reaction is spontaneous
    C. spontaneity depends on temperature
    D. the reaction is at equilibrium
    E. spontaneity depends on concentrations of reactants.
    


12. The kinetics of most enzymatic reactions can be described in terms of K_m and V_max. Which best describes K_m?
    A. the concentration of an inhibitor required to produce 50% inhibition
    B. the velocity of the reaction at saturating levels of substrate
    C. the binding affinity of inhibitor
    D. the substrate concentration required to give half maximum velocity
    E. the change in the rate when the temperature is increased by 10^oC
    


13. If the carboxyl carbon of palmitic acid (C16:0) is the number one carbon, which carbon of the original palmitate has been oxidized after the first round of b-oxidation?
    A. 1
    B. 2
    C. 3
    D. 14
    E. 16
    


14. The products of the TCA cycle in higher organisms are
    A. GTP, acetate, and NADPH
    B. ATP and CO ₂
    C. NADH, ADP and P_i
    D. FADH₂, lactate, and ATP
    E. NADH, CO ₂, GTP, and FADH₂
    


15. A mRNA contains the sequence 5˙≠-GAUCGGACUACGCU-3˙≠. Which probe would you use to verify both the presence of the gene on a genomic Southern blot as well as gene expression on a Northern blot?
    A. 5˙≠-GATCGGACTACGCT-3˙≠
    B. 5˙≠-AGCGTAGTCCGATC-3˙≠
    C. 5˙≠-TCGCATCAGGCTAG-3˙≠
    D. 5˙≠-CTAGCCTGATGCGA-3˙≠
    E. None of these will work
    


16. Which enzymes are required for gluconeogenesis but not for glycolysis?
    A. pyruvate dehydrogenase, hexokinase, triose phosphate isomerase
    B. pyruvate carboxylase, aldolase, glyceraldehydes-3-phosphate dehydrogenase
    C. pyruvate carboxylase, phosphoenolpyruvate carboxykinase, fructose-1,6-bisphosphatase
    D. pyruvate kinase, phosphofructokinase,fructose-1,6-bisphosphatase
    E. glucose-6-phosphatase,phosphoenolpyruvate carboxylase, phosphoglycerate kinase
    


17. At what pH value would you expect the electrostaic attraction between the side chains of histidine (pK_a=6.5) and glutamic acid (pK_a=4.25) in a protein be the strongest?
    A. pH=3.0
    B. pH=5.5
    C. pH=7.0
    D. pH=10.0
    E. should be the same at all pH values
    


18. Select the most oxidized 4-carbon intermediate in the citric acid cycle.
    A. oxaloacetic acid
    B. fumaric acid
    C. citric acid
    D. malic acid
    E. succinic acid