Biochemistry 3050, Spring 2014 Exam 1
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Multiple Choice (2 pnts each). Write the letter of the correct answer in the space provided AND
THEN fill in the correct Bubble on the ORANGE Scantron!
______1. The structural integrity of supramolecular complexes (assemblies) of multiple components are bonded to
each other by all of the following forces EXCEPT:
a. covalent bonds
b. van der Waals forces
c. hydrogen bonds
d. hydrophobic interactions
e. ionic interactions
______2. Membrane structures are maintained primarily by:
a. hydrophobic interactions.
b. covalent bonds.
c. hydrogen bonds.
d. non-spontaneous assembly.
e. ionic interactions.
______3. Alpha helices are stabilized primarily by:
a. hydrogen bonds between the main chain peptide bond component atoms.
b. electrostatic interactions between R-groups.
c. hydrophobic interactions between the -carbons of the main chain.
d. hydrogen bonding between the R-groups.
e. hydrophobic interactions between R-groups and the solvent water.
______4. Weak forces that create constantly forming and breaking interactions at physiological temperatures, but
cumulatively impart stability to biological structures generated by their collective activity include all EXCEPT:
a. hydrogen bonds
b. van der Waals forces
c. covalent bonds
d. ionic interactions
e. hydrophobic interactions
______5. Which of the following is a true statement about non-covalent bonds?
a. They are all the result of electron sharing.
b. Hydrogen bonds, ionic bond and hydrophobic interactions all carry a degree of
specificity while van der Waals interactions are induced.
c. All noncovalent bonds are formed between oppositely charged polar functions.
d. Van der Waals interactions are not affected by structural complementarity, while
hydrogen bonds, ionic bonds and hydrophobic interaction are affected by structural
complementarity.
e. Hydrogen, van der Waals, and hydrophobic interactions do not form linear bonds.
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Biochemistry 3050, Spring 2014 Exam 1
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______6. Which of the statements about the nature of the hydrogen bond is true?
a. The donor is a hydrogen atom bonded to a carbon.
b. The more linear the bond, the stronger the interaction.
c. The acceptor must be similar in electronegativity to hydrogen.
d. It is a type of covalent bond.
e. A hydrogen bond is weaker than van der Waals forces.
______7. Electrostatic forces
a. include ionic interactions between negatively charged carboxyl groups and
positively charged amino groups.
b. average about 2 kJ/mol in aqueous solutions.
c. typically are directional like hydrogen bonds.
d. require a precise fit like van der Waals interactions.
e. include ionic, induced dipole and permanent dipole interactions.
______8. All are true about hydrophobic interactions EXCEPT:
a. Hydrophobic interactions result from the strong tendency of water to exclude
nonpolar groups or molecules.
b. Hydrophobic interactions result because water molecules prefer the stronger
interactions that they share with one another, compared to their interactions with
nonpolar molecules.
c. Hydrophobic interactions result from hydrogen bonds between water and the
hydrophobic molecules.
d. The preferential interactions between water molecules "exclude" hydrophobic
substances from aqueous solution and drive the tendency of nonpolar molecules to
cluster together.
e. Hydrophobic interactions result in nonpolar regions of biological molecules being
buried in the molecule's interior to exclude them from the aqueous milieu.
______9. A mutation in gulonolactone oxidase results in the inability of humans to sythezize what?
a. Lysine
b. NADH
c. Ascorbic acid
d. RNA
e. None of the above
______10. Biological molecules are functionally active only within a narrow range of environmental conditions with
denaturation occurring in all EXCEPT:
a. dramatic increase in temperature.
b. change in ionic strength.
c. refrigeration.
d. addition of strong acid or base.
e. none, all will denature biological macromolecules.
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Biochemistry 3050, Spring 2014 Exam 1
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______11. All are true for prokaryotic cells EXCEPT:
a. Some have flagella.
b. They have a simple plasma or cell membrane.
c. They posses a distinct nuclear area, but no nucleus.
d. They have ribosomes, but no mitochondria.
e. All are true.
______12. A carboxylic acid at pH 7.4 would most likely form a(n) ___________ with a(n) ____________.
a. ionic interaction / amine
d. hydrogen bond / aldehyde
b. ionic interaction / ketone
e. both a and c are correct
c. hydrogen bond / alcohol
______13. Properties of water that render it so suited to its role as a medium of life include all EXCEPT:
a. Unrivaled ability to form hydrogen bonds.
b. Unusually high dielectric constant of water explains water's ability to surround
ions and increase the ions' attraction for one another.
c. Unparalleled ability to orient around nonpolar solutes to promote hydrophobic
interactions.
d. The small, but significant, tendency to form H+ and OH ions.
e. None, all are true.
______14. The unrivaled ability to form ____ hydrogen bonds per liquid water molecule is the source of the strong
intermolecular attractions unique to water.
a. 1
b. 2
c. 3
d. 4
e. 5
______15. Because of its highly polar nature, water is an excellent solvent for polar substances, but NOT for:
a. salts.
b. sugars.
c. aldehydes and ketones.
d. hydrocarbons.
e. alcohols and amines.
______16. The solvent with the highest dielectric constant in this group is:
a. water.
b. acetic acid.
c. ethanol.
d. hexane.
e. benzene.
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Biochemistry 3050, Spring 2014 Exam 1
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______17. Hydrogen bonds in ice are all EXCEPT:
a. directional.
b. straight.
c. weak.
d. responsible for the lower density of ice over liquid water.
e. holding water molecules in ice apart.
______18. Pure liquid water consists of H2O molecules:
a. held in a rigid three-dimentional network.
b. with local preference for linear geometry.
c. with large numbers of strained or broken hydrogen bonds.
d. which do not switch H-bonds readily.
e. all are true.
______19. The H-bonded water around an ionic substance tends to ____; and the H-bonded water around nonpolar
solutes tends to ____.
a. inhibit ionization, promote hydrophobic interactions
b. inhibit ionization, inhibit hydrophobic interactions
c. not impact ionization, inhibit hydrophobic interactions
d. promote ionization, not impact hydrophobic interactions
e. promote ionization, promote hydrophobic interactions
______20. Amphiphilic (amphipathic) molecules include:
a. sugars.
b. acidic amino acids.
c. inorganic salts.
d. water.
e. salts of fatty acids.
______21. In micelles:
a. polar ends form hydrophobic interactions with water.
b. nonpolar ends form hydrophilic interactions with water.
c. hydrocarbon tails form hydrophobic interactions with water.
d. polar ends are hydrophobic and nonpolar ends are hydrophilic.
e. hydrocarbon tails are excluded from the water into hydrophobic domains.
______22. Water ionizes because:
a. the smaller electronegative oxygen atom strips the electron from one of its
hydrogen atoms, leaving the proton to dissociate.
b. the larger electronegative oxygen atom strips the electron from one of its hydrogen
atoms, leaving the proton to dissociate.
c. the smaller electropositive oxygen atom strips the electron from one of its
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Biochemistry 3050, Spring 2014 Exam 1
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hydrogen atoms, leaving the proton to dissociate.
d. the larger electropositive oxygen atom strips the electron from one of its hydrogen
atoms, leaving the proton to dissociate.
e. None of the above
______23. Grapefruit juice at pH 3.2 contains about ____ times as much H+ as orange juice at pH 4.3.
a. 0.9
b. 107.5
c. 102
d. 12
e. 101
______24. pH = pKa when:
a. [A]/[HA] = 0
b. log ([A]/[HA]) = 1
c. [A] >> [HA]
d. [A] = [HA]
e. log ([HA]/[A]) = 1
______25. Which of the following weak acids would make the best buffer at pH = 5.0?
a. acetic acid (Ka = 1.74  105, pKa = 4.76)
b. H2PO4 (Ka = 1.38  107, pKa = 7.20)
c. bicarbonate (Ka = 6.3  1011, pKa = 10.24)
d. tris-hydroxymethyl aminomethane (Ka = 8.32  109, pKa = 8.07)
e. lactic acid (Ka = 1.38  104, pKa = 3.86)
______26. Which of the following statements is INCORRECT about the nature of the hydrogen bond
a. The donor is a hydrogen atom bonded d. It is a type of noncovalent bond.
to an atom that is less electronegative
than hydrogen.
b. The more linear the bond, the stronger e. All of the above statements are true
the interaction.
about the nature of the hydrogen bond
c. The acceptor is a fairly electronegative
atom containing a nonbonding pair of
electrons.
______27. The intrinsic properties of the 20 amino acids include all EXCEPT:
a. -Carbon is symmetric.
b. The capacity to polymerize.
c. Novel acid-base properties.
d. Varied structure and chemical functionality in side chains.
e. Chirality
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Biochemistry 3050, Spring 2014 Exam 1
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______28 The amino and carboxyl groups of amino acids react in a head-to-tail fashion, eliminating water, and
forming a covalent ____ linkage typically referred to as a(n) ____ bond.
a. ester, aromatic
b. anhydride, phosphoanhydride
c. amide, peptide
d. dehydration, hydrogen
e. none of the above
______29. Because peptide bond formation is thermodynamically ____, biological systems must couple peptide
bond formation to a thermodynamically ____ reaction.
a. favorable, favorable
b. unfavorable, unfavorable
c. favorable, unfavorable
d. unfavorable, favorable
e. none of the above
______30. All of the statements about the classification of these amino acids are correct EXCEPT:
a. Aspartic acid and asparagine are acidic amino acids.
b. Alanine and valine are neutral, nonpolar amino acids.
c. Serine and glutamine are polar, uncharged amino acids.
d. Lysine and arginine are basic amino acids.
e. Tyrosine and phenylalanine are aromatic amino acids.
______31. Which of the following amino acids has more than one chiral carbon?
a. serine
b. lysine
c. threonine
d. cysteine
e. aspartic acid
______32. Which of the listed amino acids is classified as a basic amino acid?
a. leucine
b. phenylalanine
c. aspartate
d. asparagine
e. lysine
______33. All of the amino acids EXCEPT ____ have both free -amino and free -carboxyl groups.
a. aspartic acid
b. proline
c. asparagine
d. lysine
e. valine
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Biochemistry 3050, Spring 2014 Exam 1
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______34. The amino acid with a side-chain pKa near neutrality and which therefore plays an important role as
proton donor and acceptor in many enzyme catalyzed reactions is:
a. histidine.
b. cysteine.
c. proline.
d. serine.
e. methionine.
______35 At which of the following pH values would histidine (pKa values of 1.8, 6.0 and 9.2) be found with a net
negative charge?
a. 1.0
b. 4.0
c. 8.0
d. 11.0
e. none of the above
______36. Glutamic acid has pKa values of 2.2, 4.3 and 9.7. Calculate the isoelectric point for glutamic acid.
a. 3.25
b. 4.3
c. 5.4
d. 7.0
e. 8.6
______37. If the pI of a peptide is 4.6, ____ might be present while ____ would probably be absent.
a. Glu / Lys
b. His / Ser
c. Arg / His
d. Asp / Gly
e. Cys / Tyr
______38. A hydrophobic interaction might occur within a protein between which of the following amino acid pairs?
a. Ser/Ile
b. Val/Leu
c. Tyr/Cys
d. Lys/Asn
e. His/Val
______39. Which of the following is classified as a neutral polar amino acid?
a. Asp
d. Ser
b. Leu
e. Trp
c. His
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Biochemistry 3050, Spring 2014 Exam 1
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______40. The peptide bond has partial ____ character.
a. hydrogen bond
b. double bond
c. triple bond
d. van der Waals bond
e. all of the above
______41. Fibrous proteins, such as collagen, have which one of the following properties?
a. Highly soluble in water.
b. Their hydrophilic residues are directed into the interior of the protein.
c. Exhibit enzymatic activity.
d. Serve structural roles in the cell.
e. Monomeric.
______42. An electrostatic interaction might occur within a protein between which of the following amino acid pairs
at typical physiological pH?
a. Ser/Asn
b. Asp/Glu
c. Arg/Cys
d. Lys/Asp
e. Val/Ile
______43 A common reaction of two cysteine residues in proteins results in the formation of ____.
a. thioester bonds
b. disulfide bonds
c. dithiol bonds
d. thioether bonds
e. none of the above
______44-Helix and -strand are components of ____ structure
a. primary
b. secondary
c. tertiary
d. quaternary
e. all are true
______45. The formation of a disulfide bond would be an example of what level of protein structure?
a. primary
b. secondary
c. tertiary
d. quaternary
e. both c and d are correct
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Biochemistry 3050, Spring 2014 Exam 1
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______46. What is the overall net charge on the peptide lys-lys-ser-glu at pH 7.0?
a. +2
b. +1
c. 0
d. 1
e. 2
______47. Collagen is an example of a(n):
a. enzyme.
b. regulatory protein.
c. transport protein.
d. storage protein.
e. structural protein.
______48. Which of the following mutations would probably be least likely to impact the function of the protein?
a. Lys to Ser
b. Ala to Asp
c. His to Pro
d. Val to Ile
e. Phe to Tyr
______49. Amino acid side chains capable of forming hydrogen bonds are usually located on the protein ____ and
form hydrogen bonds primarily with the ____.
a. surface, water solvent
b. interior, water solvent
c. surface, other amino acid side chains
d. interior, other amino acid side chains
e. all are true
______50. Electrostatic interactions among amino acid residues on proteins may be damped out by high
concentrations of:
a. water.
b. organic solvents.
c. salts.
d. heat.
e. all of the above.
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