Biochemistry Exam 1

102 Questions  I  By Andreazza
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 Biochemistry Exam 1

  
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  • 1. 
    Which statement is incorrect about the nature of the hydrogen bond?
    • A. 

      The donor is a hydrogen atom bonded to a less electronegative atom than hydrogen.

    • B. 

      The more linear the bond, the stronger the interaction.

    • C. 

      The acceptor is a fairly electronegative atom containing a nonbonding pair of electrons.

    • D. 

      It is a type of noncovalent bond.


  • 2. 
    If equal molar amounts of Na2HPO4 and Na3PO4 are mixed in water, calculate the resulting pH. The pKas of phosphoric acid are 2.1, 7.2, 12.4.
    • A. 

      7.0

    • B. 

      12.4

    • C. 

      4.5

    • D. 

      9.5


  • 3. 
    Which of the following characteristics is not associated with the solvent water?
    • A. 

      High surface tension

    • B. 

      A chemically inert solvent, which has a great capability to dissolve a diverse spectrum of molecules and ions

    • C. 

      Low heat capacity

    • D. 

      A high dielectric constant


  • 4. 
    Which of the following amino acids is the least water soluble at pH 7.0?
    • A. 

      Tryptophan

    • B. 

      Glutamic acid

    • C. 

      Cysteine

    • D. 

      Histidine


  • 5. 
    Which amino acid would migrate the furthest toward the anode (positive electrode) during paper electrophoresis at pH 7.0?
    • A. 

      Aspartic acid

    • B. 

      Alanine

    • C. 

      Lysine

    • D. 

      Glutamine


  • 6. 
    Calculate the pH that results when 0.75 mmol of HCl is added to 1.0 mmol of isoelectric histidine in 100 ml of water. The pKas for histidine are 1.8, 6.0, and 9.2.
    • A. 

      6.5

    • B. 

      6.0

    • C. 

      8.8

    • D. 

      5.5


  • 7. 
    What volume of 2 N HCl is required to completely titrate a 4 mmol monosodium aspartate (Asp.Na) solution? For Asp.Na to be completely titrated we need 2 mols of HCl per mol of Asp.Na or 8mmolof HCl per 4mmol of Asp.Na.  mmol HCl = VHClxNHCl or V = 8mmol/2M = 
    • A. 

      2 ml

    • B. 

      3 ml

    • C. 

      4 ml

    • D. 

      6 ml or more


  • 8. 
    Quaternary structure is associated with
    • A. 

      The overall shape of a polypeptide chain

    • B. 

      The sum of the secondary and tertiary interactions

    • C. 

      Simple proteins with only one subunit

    • D. 

      The relative orientation of one polypeptide to another polypeptide in a multi-subunit protein


  • 9. 
    Reaction of the peptide, ala-met-lys-ser, with phenylisothiocyanate (PITC) at pH 8.0 followed by mild acidification (first cycle of Edman chemistry):  
    • A. 

      Would release the labeled peptide PTH-ala-met-lys-ser

    • B. 

      Would release PTH-ala, PTH-ser, PTH-lys, and PTH-ser

    • C. 

      Would release PTH-ser and the peptide ala-met-lys

    • D. 

      Would release PTH-ala and the peptide met-lys-ser


  • 10. 
    Which factors will influence the native conformation of a protein?
    • A. 

      PH of the solution

    • B. 

      Concentration of salt in solution

    • C. 

      Its sequence of amino acids

    • D. 

      All of the above


  • 11. 
    The repeating secondary structures as found in beta-strands, beta-turns, and alpha-helices of folded proteins primarily result from
    • A. 

      Hydrogen bonds

    • B. 

      Electrostatic interactions

    • C. 

      Hydrophobic interactions

    • D. 

      Van der Waals interactions


  • 12. 
    Covalent forces
    • A. 

      Are intramolecular forces

    • B. 

      Are intermolecular forces

    • C. 

      Are both intra and intermolecular forces

    • D. 

      None of the above


  • 13. 
    Living systems are characterized by these, EXCEPT
    • A. 

      Organisms are complicated and highly organized

    • B. 

      Biological structures serve functional purposes

    • C. 

      Living systems are always at equilibrium

    • D. 

      Living systems are able to replicable


  • 14. 
    Carbon is essential for life is because
    • A. 

      It has four bonds

    • B. 

      It makes versatile, complex structures

    • C. 

      It can be used to make CO2

    • D. 

      None of the above


  • 15. 
    One of these bonds is not capable of hydrogen bonding
    • A. 

      C-H

    • B. 

      O-H

    • C. 

      N-H

    • D. 

      F-H


  • 16. 
    Oil in water
    • A. 

      Organizes the water molecules

    • B. 

      Disorganize the water molecules

    • C. 

      Make water stable

    • D. 

      None of the above


  • 17. 
    The pH of a 0.05M solution of Ca(OH)2 is 
    • A. 

      1

    • B. 

      13

    • C. 

      -1.3

    • D. 

      5


  • 18. 
    The ionization constant of pure water is
    • A. 

      1 x 10^-7

    • B. 

      1 x 10^7

    • C. 

      1 x 10^-14

    • D. 

      1 x 10^14


  • 19. 
    Which of the following pKAs represents the strongest acid?
    • A. 

      3

    • B. 

      6

    • C. 

      5

    • D. 

      10


  • 20. 
    For a weak acid and its conjugated base the following is true
    • A. 

      KAH x KA- = 10^-14

    • B. 

      PH = pKa + Log [A-]/[AH]

    • C. 

      PKa + pKb = 14

    • D. 

      All are true


  • 21. 
    If equal volumes of 0.8M sodium lactate and 0.4M lactic acid are mixed, and the pKa of lactic acid is 3.86, the final of the solution pH should be
    • A. 

      3.86

    • B. 

      Higher than 3.86

    • C. 

      Lower than 3.86

    • D. 

      Neutral


  • 22. 
    What would be the resulting pH following addition of 0.5 moles of sodium hydroxide to 1.0 mole of isoelectric alanine? The pKas for alanine are 2.4 and 9.7.
    • A. 

      2.4

    • B. 

      6.0

    • C. 

      9.7

    • D. 

      12.0


  • 23. 
    The organ that controls the pH of the small intestine is?
    • A. 

      Gallbladder

    • B. 

      Kidneys

    • C. 

      Pancreas

    • D. 

      Liver


  • 24. 
    Which statement is INCORRECT about the classification of amino acids?
    • A. 

      Alanine and valine are neutral, nonpolar amino acids

    • B. 

      Tryptophan and phenylalanine are aromatic amino acids

    • C. 

      Lysine and arginine are basic amino acids

    • D. 

      Aspartic acid and asparagine are acidic amino acids


  • 25. 
    An isoelectric amino acid was dissolved in water and the resulting pH was approximately 7.6. What amino acid would possess this property?
    • A. 

      Alanine

    • B. 

      Glutamic acid

    • C. 

      Histidine

    • D. 

      Lysine


  • 26. 
    Which of the following peptides would absorb the most light centered at 280 nm?
    • A. 

      Trp-tyr-thr-lys-phe

    • B. 

      Lys-ala-trp-trp-val

    • C. 

      Thr-thr-phe-tyr-lys

    • D. 

      Tyr-thr-va-thr-thr


  • 27. 
    For the amino acids histidine, alanine, and aspartic acid, list the amino acids in order of increasing isoelectric points.
    • A. 

      Ala, his, asp

    • B. 

      Asp, ala, his

    • C. 

      His, ala, asp

    • D. 

      Ala, asp, his


  • 28. 
    An isoelectric amino acid was dissolved in water and the resulting pH was approximately 10.7 . What amino acid would possess this property?
    • A. 

      Arginine

    • B. 

      Glutamic acid

    • C. 

      Histidine

    • D. 

      Lysine


  • 29. 
    Which statement is CORRECT about the peptide ala-ser?
    • A. 

      Alanine is at the N-terminal of the peptide

    • B. 

      There are a total of six atoms that lie in the plane of the peptide bond linking alanine to serine

    • C. 

      The alpha-carbon of alanine is sp3 hybridized

    • D. 

      All the above are correct statements


  • 30. 
    Fibrous proteins, such as collagen, have which 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


  • 31. 
    The tertiary structure of a protein is usually a result of which of the following interactions?
    • A. 

      Intramolecular hydrogen bonding

    • B. 

      Electrostatic interactions

    • C. 

      Hydrophobic interactions

    • D. 

      All of the above interactions


  • 32. 
    The information needed to define the structure of a protein is essentially contained in
    • A. 

      Amino acid composition

    • B. 

      Amino acid sequence

    • C. 

      Secondary structure

    • D. 

      Tertiary structure


  • 33. 
    Determine the amino acid sequence of the following oligopeptide from the experimental data below 1. The amino acid composition is found to be ala, lys, phe, met, cys, trp 2. Treatment with carboxypeptidase results in tryptophan and a peptide 3. CNBr treatment yields a tetrapeptide and a dipeptide 4. Trypsin digestion produces an amino acid and a pentapeptide with met on the amino end 5. Chymotrypsin digestion yields a dipeptide and a tetrapeptide
    • A. 

      Trp-lys-met-cys-met-ala

    • B. 

      Lys-ala-cys-phe-met-trp

    • C. 

      Trp-ala-phe-cys-met-lys

    • D. 

      Lys-met-cys-phe-ala-trp


  • 34. 
    If the following section of a polypeptide is folded into an alpha-helix, to which amino acid is the CARBONYL GROUP OF ALANINE noncovalently bonded? ala-ser-val-asp-glu-leu-gly
    • A. 

      Serine

    • B. 

      Glutamic acid

    • C. 

      Aspartic acid

    • D. 

      Leucine


  • 35. 
    What in incorrect about an alpha-helix?
    • A. 

      The helix has a left handed pitch

    • B. 

      The helix has 3.6 amino acids per turn

    • C. 

      The helix is right handed

    • D. 

      The helix possesses an overall dipole moment


  • 36. 
    One of these is not used to separate the subunits in a protein
    • A. 

      6 M guanidine HCl

    • B. 

      High salt concentration

    • C. 

      Chymotrypsin

    • D. 

      8M urea


  • 37. 
    One of these is not found in alpha helices
    • A. 

      Methionine

    • B. 

      Lysine

    • C. 

      Aspartic acid

    • D. 

      Proline


  • 38. 
    Iodoacetate is used to
    • A. 

      Acetylate enzymes

    • B. 

      Iodinate proteins

    • C. 

      Block sulfidryl (thiol) groups

    • D. 

      None of the above


  • 39. 
    The energy that ATP transfers to another molecule resides in the phosphate bonds. 
    • A. 

      True

    • B. 

      False


  • 40. 
    The type of energy released in an exergonic reaction is known as activation energy. 
    • A. 

      True

    • B. 

      False


  • 41. 
    Specific binding is a characteristic of the diverse molecules such as enzymes. 
    • A. 

      True

    • B. 

      False


  • 42. 
    Living systems are not actively engaged in energy transformations.
    • A. 

      True

    • B. 

      False


  • 43. 
    Our bones are composed mainly of weak intermolecular forces. 
    • A. 

      True

    • B. 

      False


  • 44. 
    Calculate the net energy of electrolysis of water: 2H20(l) → 2H2(g) + O2(g)
    • A. 

      +566 kJ/mol

    • B. 

      +56 kJ/mol

    • C. 

      +5.6 kJ/mol

    • D. 

      None of the above


  • 45. 
    What type of forces stabilizes the biological structure of macromolecules? Are covalent bonds weaker than these interactions? 
    • A. 

      Weak forces stabilize the biological structure of macromolecules. Covalent bonds are stronger.

    • B. 

      Weak forces stabilize the biological structure of macromolecules. Covalent bonds are weaker.

    • C. 

      Strong forces stabilize the biological structure of macromolecules. Covalent bonds are stronger.

    • D. 

      Strong forces stabilize the biological structure of macromolecules. Covalent bonds are weaker.


  • 46. 
    Which of the following statements is true:
    • A. 

      Ion-ion strong interactions are mainly found in blood.

    • B. 

      London dispersion forces may be found in every type of interaction.

    • C. 

      There is only one type of ion-ion interaction.

    • D. 

      B and c are correct

    • E. 

      None of the above


  • 47. 
    Based on the properties of Hydrogen “bond”, put pentane, water and ethanol in order of their boiling points (from strongest to weakest).  Hint: these may or may not create H-bonds with their own molecules.
    • A. 

      Water > ethanol > pentane

    • B. 

      Ethanol>pentane>water

    • C. 

      Water< ethanol

    • D. 

      Ethanol


  • 48. 
    Oxygen in water is a type of dipole-induced dipole.
    • A. 

      True

    • B. 

      False


  • 49. 
    A Hydrogen atom interacts with a very electronegative atom to form an H-bond. 
    • A. 

      True

    • B. 

      False


  • 50. 
    Living organisms can function better with Si-O than C-O bonds.
    • A. 

      True

    • B. 

      False


  • 51. 
    When Water is mixed with a non-polar solute, its entropy increases. 
    • A. 

      True

    • B. 

      False


  • 52. 
    Water is an amphipathic molecule. 
    • A. 

      True

    • B. 

      False


  • 53. 
    Weak forces bind free atoms together. 
    • A. 

      True

    • B. 

      False


  • 54. 
    When HCl (strong acid) is added to water, the entropy will increase
    • A. 

      True

    • B. 

      False


  • 55. 
    Detergent actually allows the surface tension of water to increase. 
    • A. 

      True

    • B. 

      False


  • 56. 
    The more undisocciated the acid, the stronger it is. 
    • A. 

      True

    • B. 

      False


  • 57. 
    What is the pH of 4.5 x 10-3 M solution of Ba(OH)2? Hint: Ba(OH)2→Ba+2 + 2OH-. Concentration of OH- is twice the concentration in Ba(OH)2.   2(4.5 x 10-3) = 9 x 10-3 = [OH-], [H+] = [1 x 10-14] / [9 x 10-3], [H+] = 1.1 x 10-12      Therefore, pH = -log[H+]   pH = -log (1.1 x 10-12)    pH = ________
    • A. 

      11.95

    • B. 

      1.95

    • C. 

      9.95

    • D. 

      6.95


  • 58. 
    If the ratio of [HPO4-2] / [H2PO4-] in a muscle cell is 0.39, what is the internal pH of this cell? Hint: Phosphoric acid (H3P04) has three pKas (check powerpoint or textbook Chap 2). Choose only one pKa according to [HPO4-2] / [H2PO4-]. pH = pKa + log [A-]/[HA] pH = 7.2 + log (0.39) → pH = __________
    • A. 

      6.79

    • B. 

      4.79

    • C. 

      12.79

    • D. 

      2.79


  • 59. 
    _____________ interactions are vital for cell membranes. 

  • 60. 
    Micelles contain __________ends in contact with water and _________ends in the center. (answer, answer)

  • 61. 
    As the ______ of a strong acid is a high value, its ______ should be low. (answer, answer)

  • 62. 
    As an acid or a base is added, ___________ solutions will not easily change pH.

  • 63. 
    The Henderson-Hasselbalch equation states that pH =______ when there are equal amounts or equivalents of an acid and its conjugate base.

  • 64. 
    Which component in an amino acid will determine its identity?
    • A. 

      The R-group

    • B. 

      Temperature

    • C. 

      Polarity

    • D. 

      None of the above


  • 65. 
    Is hydration used to bind two amino acids? 
    • A. 

      Yes, hydration is used to bind two amino acids

    • B. 

      No, dehydration is used to bind two amino acids


  • 66. 
    At what pH an amino acid will be neutral in charge, without considering any ionization on the side chain? 

  • 67. 
    How do you call a neutral amino acid? 

  • 68. 
    There are four aromatic amino acids. 
    • A. 

      True

    • B. 

      False


  • 69. 
    All twenty amino acids are chiral. 
    • A. 

      True

    • B. 

      False


  • 70. 
    At neutral pH, amino acids can be positively or negatively charged. 
    • A. 

      True

    • B. 

      False


  • 71. 
    In acidic conditions, amino groups will be protonated
    • A. 

      True

    • B. 

      False


  • 72. 
    In basic conditions, Phe will be neutrally charged. 
    • A. 

      True

    • B. 

      False


  • 73. 
    At pH = 14, glutamic acid is in cationic form.
    • A. 

      True

    • B. 

      False


  • 74. 
    At pH = 1, the R group of acidic and basic amino acids are charged.
    • A. 

      True

    • B. 

      False, neither acidic nor basic are charged

    • C. 

      False, only acidic are charged

    • D. 

      False, only basic are charged


  • 75. 
    At pKa value of an amino acid, there are equal amounts of acid and conj. base. 
    • A. 

      True

    • B. 

      False


  • 76. 
    If the side group of Glu is ¾ dissociated, its pH is around 1.523 
    • A. 

      True

    • B. 

      False


  • 77. 
    In a sequence of six residues, there are five peptide bonds. 
    • A. 

      True

    • B. 

      False


  • 78. 
    Ala-Gly-Lys-Gln-Arg-Phe-Asp Hint: sense of directionality for peptide bond COO - →NH3+ What amino acids are the N-terminal and C-terminal? 
    • A. 

      N is Ala. C is Asp.

    • B. 

      N is Asp. C is Ala.

    • C. 

      There is no terminal

    • D. 

      There is only N-terminal Asp


  • 79. 
    Ala-Gly-Lys-Gln-Arg-Phe-Asp Hint: sense of directionality for peptide bond COO - →NH3+ How many pKa values does this peptide have? 
    • A. 

      3

    • B. 

      4

    • C. 

      5

    • D. 

      0


  • 80. 
    Ala-Gly-Lys-Gln-Arg-Phe-Asp Hint: sense of directionality for peptide bond COO - →NH3+ What is the net charge of this peptide at pH = 6? 
    • A. 

      -2

    • B. 

      -1

    • C. 

      0

    • D. 

      +1


  • 81. 
    In a cation exchange bead: The bead will be mainly positively or negatively charged? 
    • A. 

      Positively charged

    • B. 

      Negatively charged


  • 82. 
    In a cation exchange bead: A mixture of His, Glu and Arg is added. Which one will elute first at pH = 5? 
    • A. 

      His

    • B. 

      Glu

    • C. 

      Arg

    • D. 

      They all elute at the same time.


  • 83. 
    In a cation exchange bead: A mixture of His, Glu and Arg is added. One will elute first at pH = 5. If pH is increased to 7, which amino acid will be eluted next? 
    • A. 

      His

    • B. 

      Glu

    • C. 

      Arg

    • D. 

      Both A & C


  • 84. 
    The pI of Arg can be found by taking the average of its first two pKa values. 
    • A. 

      True

    • B. 

      False


  • 85. 
    The main function of iodoacetate is to promote the formation of disulfide bridges
    • A. 

      True

    • B. 

      False


  • 86. 
    Ellman’s reagent is used to determine the concentration of thiol groups in a sample. 
    • A. 

      True

    • B. 

      False


  • 87. 
    Edman’s reagent will modify the C-terminal residues of a peptide sequence. 
    • A. 

      True

    • B. 

      False


  • 88. 
    Chymotrypsin mainly cleaves amino acids which absorb light at 260-280nm. 
    • A. 

      True

    • B. 

      False


  • 89. 
    The presence of proteins can be determined when the solution turns purple. 
    • A. 

      True

    • B. 

      False


  • 90. 
    The partial double bond character of a peptide bond allows free rotation. 
    • A. 

      True

    • B. 

      False


  • 91. 
    In HPLC, amino acids are separated mainly based on their charges.
    • A. 

      True

    • B. 

      False


  • 92. 
    A multimeric protein contains a few (~3) disulfide bridges. After treating it with 8M urea to separate amino acid chains, iodoacetate should be added next. 
    • A. 

      True

    • B. 

      False


  • 93. 
    One way to determine the C terminal is by using carboxypeptidases. 
    • A. 

      True

    • B. 

      False


  • 94. 

    What is this derivative called? 

  • 95. 

    What reagent has been used?

  • 96. 

    What type of analysis has been done? 

  • 97. 

    What is the amino acid that has being modified

  • 98. 
    Gly-Met-Asp-Phe-Lys-Tyr-Met-Glu-Arg   Which of the following reagents will cleave this peptide into two fragments only?
    • A. 

      Trypsine

    • B. 

      Chymotrypsin

    • C. 

      Cyanogen bromide

    • D. 

      Staphylococcal V8 protease


  • 99. 
    Gly-Met-Asp-Phe-Lys-Tyr-Met-Glu-Arg Which of the above reagents will produce a peptide with a C-terminal homoserine lactone? And how many fragments will be produced?
    • A. 

      Cyanogen bromide, 3 fragments

    • B. 

      Cyanogen bromide, 2 fragments

    • C. 

      Trypsin, 3 fragments

    • D. 

      Trypsin, 2 fragments


  • 100. 
    Gly-Met-Asp-Phe-Lys-Tyr-Met-Glu-Arg What happens if Clostripain and Carboxypeptidase A are added?
    • A. 

      All amino acids will be cut

    • B. 

      All amino acids will be cut, except for Arginine and Lysine

    • C. 

      Nothing will happen


  • 101. 
    Gly-Met-Asp-Phe-Lys-Tyr-Met-Glu-Arg After 3 rounds with Edman’s reagent, which residue will be modified next with this same reagent?
    • A. 

      Asp

    • B. 

      Phe

    • C. 

      Met

    • D. 

      Tyr


  • 102. 
    1. Amino acid analysis of a peptide shows the composition Ala5, Lys1, Phe1. 2. Reaction of the intact peptide with Edman’s reagent followed by acid hydrolysis liberates Ala. 3. Trypsin cleavage of the intact peptide gives a tripeptide and a tetrapeptide with compositions Ala3, Phe1 and Lys1, Ala2. 4. Reaction of the intact peptide with chymotrypsin yields a hexapeptide plus free Ala. What is the sequence of this peptide?  
    • A. 

      Ala-Ala-Lys-Ala-Ala-Phe-Ala

    • B. 

      Ala-Ala-Ala-Ala-Lys-Phe-Ala

    • C. 

      Ala-Phe-Lys-Ala-Ala-Ala-Ala

    • D. 

      Ala-Lys-Ala-Ala-Ala-Ala-Phe


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