UNIT 1 EXAM - PRACTICE

Question 1

An exergonic process:

A. requires energy to proceed.
B. has a ΔG > 0.
C. must have a ΔH < 0.
D. requires an increase in entropy to occur during the reaction.
E. can sometimes have ΔH > 0.

Answer 1

E. can sometimes have ΔH > 0.

Question 2

50 mL of 120 mM NaCI is added to 100 mL of water. What is the final concentration of NaCI in this solution?

A. 10 mM
B. 40 mM
C. 50 mM
D. 60 mM
E. None of the above

Answer 2

B. 40 mM

Question 3

A non-covalent interaction between an amine and an alcohol would likely involve which of the following?

A. Salt bridges (ionic interactions)
B. Hydrophobic interactions
C. Hydrogen bonding
D. Covalent bonding
E. None of the above

Answer 3

C. Hydrogen bonding

Question 4

Which of the following compounds can act as a buffer?

A. Glycine
B. Arginine
C. Sodium acetate
D. All of the above
E. None of the above

Answer 4

D. All of the above

Question 5

The most important extracellular buffering system (acid-base pair) is

A. H2CO3 / HCO^3-
B. HCO3- / СО3^2-
С. H3PO4 / H2PO4
D. H2PO4 / HPO4^2-
E. HPO4^2- / PO4^3-

Answer 5

A. H2CO3 / HCO^3-

Question 6

Which solution would undergo the smallest change in pH upon addition of HCI to a final concentration of 10 mM? The pKa of sodium acetate is 4.76.

A. 100 mM sodium acetate pH 3
B. 50 mM sodium acetate pH 4.86
C. 50 mM sodium acetate pH 4.66
D. 10 mM sodium acetate pH 5
E. 10 mM sodium acetate pH 3

Answer 6

B. 50 mM sodium acetate pH 4.86

Question 7

The melting temperature of DNA:

A. is the temperature at which double stranded DNA is completely denatured.
B. is used to measure gene expression.
C. cannot be accurately measured.
D. depends only on the length of complementary DNA and not its composition.
E. increases with increased GC content in the DNA.

Answer 7

E. increases with increased GC content in the DNA.

Question 8

A single nucleotide (base) substitution in the exon of a gene could result in any of the following consequences EXCEPT:

A. A conservative amino acid substitution in the encoded protein.
B. A non-conservative amino acid substitution in the encoded protein.
C. A nonsense mutation.
D. A shift in the reading frame, resulting in altered C-terminal sequence.
E. No apparent effect on the structure or function of the encoded protein.

Answer 8

D. A shift in the reading frame, resulting in altered C-terminal sequence.

Question 9

Which of the following amino acids can be used to quantify proteins due to their absorbance of
UV light?

A. Trp and Tyr
B. Trp and Thr
C. Tyr and Pro
D. Trp and Arg
E. Pro and Lys

Answer 9

A. Trp and Tyr

Question 10

When a protein folds…?

A. B-sheets always form.
B. it cannot be unfolded if disulfide bonds are created.
C. it must sample all possible orientations while it folds.
D. secondary structures are one of the first structural elements to form.
E. None of the above

Answer 10

D. secondary structures are one of the first structural elements to form.

Question 10

13. The addition of urea can greatly weaken hydrogen bonding in proteins. This may result in:

A. stabilization of protein tertiary structure.
B. disruption of a-helices and b-sheets.
C. a decrease in the pH of the solution.
D. increased strength of the hydrophobic effect.
E. no change to protein tertiary structure.

Answer 10

B. disruption of a-helices and b-sheets.

Question 11

In cation exchange chromatography, ______ resin separates proteins based on their ________.

A. positively charged; size
B. negatively charged; surface charge
C. positively charged; surface charge
D. ligand bound resin; function
E. porous resin; surface charge

Answer 11

B. negatively charged; surface charge

Question 12

15. Which of the below statements is true?

A. In size exclusion chromatography the largest molecules enter the beads and elute last.
B. Anion exchange chromatography separates proteins by size.
C. Proteins containing a 6x histidine tag can bind to immobilized Ni2+
D. The 3D structure of a protein can only be determined by X-ray crystallography.
E. All proteins must absorb light at 280 nm.

Answer 12

C. Proteins containing a 6x histidine tag can bind to immobilized Ni2+

Question 13

_______ is used for oxygen storage and has a _________ oxygen dissociation curve.

A. myoglobin; hyperbolic
B. myoglobin; sigmoidal
C. hemoglobin; hyperbolic
D. hemoglobin; sigmoidal
E. myoglobin; logarithmic

Answer 13

A. myoglobin; hyperbolic

Question 14

Fly myoglobin has a Pso of 10 m Torr. Which of the following statements must be true?

A. Fly myoglobin displays cooperative oxygen binding.
B. Fly myoglobin is a heterodimer.
C. The proximal histidine of fly myoglobin is destabilized.
D. When pO2 equals 50 m Torr fly myoglobin is over 80% saturated with 02.
E. When pOz equals 5 Torr fly myoglobin is 50% saturated with oxygen.

Answer 14

D. When pO2 equals 50 m Torr fly myoglobin is over 80% saturated with 02.

Question 15

In collagen…

A. alpha-helices coil together to form a fiber.
B. cysteine provides crosslinks between collagen fibers.
C. aromatic amino acids hold the fiber together.
D. proline is not important.
E. glycine is required at every third residue because it is the smallest amino acid.

Answer 15

E. glycine is required at every third residue because it is the smallest amino acid.

Question 16

A common feature of both actin (micro)filaments and microtubules is that they..?

A. both utilize GTP to regulate filament assembly and disassembly.
B. are both components of the cytoskeleton.
C. both normally polymerize and depolymerize from the same end of the filament.
D. both consist of globular actin subunits.
E. are both organized at the centrosome.

Answer 16

B. are both components of the cytoskeleton.

Question 17

Mutation of valine and isoleucine residues to serine would most likely destabilize keratin by

A. destabilizing the a-helix.
B. creating steric clashes between adjacent residues.
C. causing aggregation due to loss of the hydrophobic effect.
D. destabilizing the triple helix.
E. reducing the stability of the coiled-coil

Answer 17

E. reducing the stability of the coiled-coil