Bio-479 Chapter 4

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Bio-479 Chapter 4
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2013-10-14 12:01:50
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  1. Thyroxine 

    -Plays a role in cellular metabolism.
    -An iodine-containing thyroid hormone.
    -Neurotransmitter.
    -Mediator of allergic reactions.
     
    -An iodine-containing thyroid hormone.
  2. The Fischer convention is well suited for describing molecules with multiple chiral centers.

    True or False ?
    False , Fischer convention is best suited for describing molecules with one chiral center.
  3. Lysine has pK values of 2.16, 9.06, and 10.54, for its carboxyl, -amino, and -amino groups, respectively. What is its estimated pI?

    -9.06
    -9.80
    -6.85
    -5.66
    9.80
  4. Which amino acid side chain is considered nonpolar?

    Glutamine
    Histidine
    Isoleucine
    Tyrosine
    Isoleucine
  5. Which amino acid side chain can form a hydrogen bond?

    Isoleucine
    Alanine
    Glycine
    Threonine
    Threonine
  6. Methionine is the only amino acid that contains sulfur.

    False or True ?
    False , methionine and cysteine  both have Sulfur groups
  7. By convention the amino terminal residue of a peptide chain is written as the right-most residue.

    True or False ?
    False , N-terminus is the left most and C-terminus is the right most.
  8. The alpha-amino groups of all amino acids have a  charge (+ or -) at pH 7.
    positive (+)
  9. The polymerization of amino acids to form a polypeptide can be represented as a ______ reaction.
    condensation
  10. _______ is the only amino acid of the 20 standard amino acids that lacks a primary amine.
    proline
  11. Aspartic Acid

    Side chain is -CH2-SH.
    Side chain is -CH2COOH.
    Side chain is -CH3.
    Side chain is -CH2OH.
    Side chain is -H.
    Side chain is -CH2-phenyl.
    Side chain is -CH2-CH2-S-CH3.
    Side chain is -CH2-CH2-CH2-CH2-NH2.
    Side chain is -CH2COOH.
  12. Serine

    Side chain is -CH2COOH.
    Side chain is -CH2-phenyl.
    Side chain is -CH2-CH2-CH2-CH2-NH2.
    Side chain is -CH2OH.
    Side chain is -CH3.
    Side chain is -CH2-CH2-S-CH3.
    Side chain is -H.
    Side chain is -CH2-SH.
    Side chain is -CH2OH.
  13. Methionine

    Side chain is -CH3.
    Side chain is -CH2-SH.
    Side chain is -CH2-phenyl.
    Side chain is -CH2OH.
    Side chain is -CH2-CH2-CH2-CH2-NH2.
    Side chain is -CH2-CH2-S-CH3.
    Side chain is -H.Side chain is -CH2COOH
    Side chain is -CH2-CH2-S-CH3.
  14. Identify the side chain of each item listed:Glycine

    Side chain is -CH2-phenyl.
    Side chain is -H.
    Side chain is -CH2COOH.
    Side chain is -CH2-SH.
    Side chain is -CH2OH.
    Side chain is -CH3.
    Side chain is -CH2-CH2-S-CH3.
    Side chain is -CH2-CH2-CH2-CH2-NH2
    Side chain is -H.
  15. Molecules that are nonsuperimposable mirror images are known as _________ of each other.

    diastereomers
    enantiomers
    zwitterions
    racemers
    enantiomers
  16. What is the net overall charge on glutamic acid at pH 12.
    -2
  17. What is the net charge on the amino acid lysine at pH 7.
     
    +1
  18. The Fischer convention is commonly used to describe the stereochemistry of amino acids. In the Fischer convention, the configuration of the groups around an asymmetric center is compared to that of glyceraldehyde, a molecule with one asymmetric center. For e.g., L-glyceraldehyde and L-amino acids are said to have the same relative configuration.

    True or False ?
    True
  19. Many drugs are chemically synthesized as racemic mixtures, although only one enantiomer has biological activity.

    True or False ?
    True
  20. Proline can be modified by the addition of a hydroxy group.

    True or False ?
    True
  21. Most peptides containing D-amino acids are not synthesized by the standard protein synthetic machinery.

    True or False ?
     
    True
  22. A tripeptide that helps inactivate oxidative compounds is
    glutathione
  23. Some types of nonstandard amino acids are not generally found in polypeptides.

    True or False ?
    True
  24. Modification of amino acids in proteins is rarely important for function.

    True or False ?
    False
  25. All standard amino acids except glycine have one asymmetric carbon.

    False or True ?
    False  , All standard amino acids except glycine have one or more asymmetric carbons. Isoleucine and threonine have two asymmetric carbons.
  26. D-amino acids are found in the short polypeptides of some _____  cell walls.
    bacterial
  27. All standard amino acids, except _______  have a chiral alpha carbon
    glycine
  28. Why is the pK of the carboxyl group of glycine (2.35) so much lower than that of acetic acid (4.76)?
    Because the positively-charged amino group of glycine stabilizes the carboxylate group
  29. Glutamic acid has pK values of 2.10, 4.07, and 9.47 for its -carboxyl group, -carboxyl group, and -amino group, respectively. What is its estimated pI?

    5.785
    3.085
    4.07
    6.77
    3.085
  30. Glutamine has pK values of 2.17 and 9.13. What is its estimated pI?

    2.17
    5.65
    7.00
    9.13
    5.65
  31. Which amino acid side chain is the least flexible?

    Leucine
    Lysine
    Proline
    Methionine
    Proline
  32. Which amino acid side chain is most likely to be positively charged at pH 7?

    Serine
    Tyrosine
    Arginine
    Aspartic acid
    Arginine
  33. Which amino acid side chain is considered polar?

    Serine
    Valine
    Phenylalanine
    Methionine
    Serine
  34. Glutamine can be converted into which amino acid by acid hydrolysis?

    Glutamic acid
    Asparagine
    Arginine
    Aspartic acid
    Glutamic acid
  35. Which amino acid side chain forms disulfide bonds?
    Histidine
    Lysine
    Cysteine
    Methionine
    Cysteine
  36. Which amino acid side chain is aromatic?

    Alanine
    Phenylalanine
    Threonine
    Glutamic acid
    Phenylalanine
  37. Which amino acid side chain cannot ionize?

    Histidine
    Aspartic acid
    Asparagine
    Cysteine
    Asparagine
  38. Which amino acid side chain cannot form a hydrogen bond?

    Tryptophan
    Glutamine
    Valine
    Tyrosine
    Valine
  39. The pI of any amino acid can be estimated by the average of the pK values of the -amino group and the -carboxyl group.

    True or False ?
    False
  40. Almost all amino acids have ionizable side chains.

    True or False ?
    False
  41. Leucine and alanine have large, nonpolar side chains.

    True or False ?
    False
  42. Serine and valine have polar, uncharged side chains.

    True or False ?
    False
  43. The condensation of two amino acids yields a peptide and a molecule of water.

    False or True ?
    True
  44. By convention, polypeptide chains are named from left to right beginning with the amino acid at the (N or C ) -terminus.
    N
  45. The carboxylic groups of all amino acids have a_______  charge at pH 7.
    negative
  46. The_______  point is the pH at which a molecule has no net charge.
    isoelectric
  47. Amino acids that are incorporated into a polypeptide chain are referred to as amino acid _______
    residues
  48. Tryptophan

    Side chain contains phenol group.
    Side chain contains indole group.
    Side chain contains guanidino group.
    Side chain contains isopropyl group.
    Side chain contains imidazole group.
    Side chain contains sulfhydryl group.
    Indole
  49. Valine
    Side chain contains indole group.
    Side chain contains imidazole group.
    Side chain contains guanidino group.
    Side chain contains sulfhydryl group.
    Side chain contains phenol group.
    Side chain contains isopropyl group.
    isopropyl group
  50. Tyrosine

    Side chain contains guanidino group.
    Side chain contains sulfhydryl group.
    Side chain contains isopropyl group.
    Side chain contains phenol group.
    Side chain contains imidazole group.
    Side chain contains indole group
    phenol group
  51. Cysteine

    Side chain contains isopropyl group.
    Side chain contains phenol group.
    Side chain contains imidazole group.
    Side chain contains indole group.
    Side chain contains guanidino group.
    Side chain contains sulfhydryl group.
    Side chain contains sulfhydryl group.
  52. Arginine

    Side chain contains imidazole group.
    Side chain contains indole group.
    Side chain contains guanidino group.
    Side chain contains sulfhydryl group.
    Side chain contains phenol group.
    Side chain contains isopropyl group.
    guanidino group
  53. Histidine

    Side chain contains indole group.
    Side chain contains isopropyl group.
    Side chain contains imidazole group.
    Side chain contains guanidino group.
    Side chain contains sulfhydryl group.
    Side chain contains phenol group.
    Imidazole group
  54. How many functional groups does the peptide MDFGRKCDE have that can be titrated?

    5
    7
    8
    6
    8
  55. Which amino acid(s) could be used to make a buffer at pH 4.0?

    Asp

    Gln

    Glu

    Asp and Gln

    Asp and Glu
    Asp and Glu
  56. Which of the 20 standard amino acids is not optically active (chiral) and why?
     
    • Glycine, because its side chain is a hydrogen atom.
    •  
  57. How many charged groups do ALL isolated amino acids have at physiological pH?

    1
    more than 1
    more than 2
    Not all amino acids are charged
    more than 1
  58. There are several amino acid side chains which are always charged at physiological pH. These are:

    Glu, Asp, Lys, and His.
    Gln, Asn, Glu, and Asp.
    Glu, Lys, Asp, His, and Arg.
    Glu, Asp, Lys, and Arg.
    none of the above.
    Glu, Asp, Lys, and Arg.

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