Biochem Chapter 6 EXAM 4

BIOCHEM CHAPTER 6 EXAM 3
Which one of the following statements about peptide bonds is FALSE. Peptide bonds
are:
-charged.
-covalent.
-involved in forming the primary structure of proteins.
-amides.
-rigid and planar, with partial double-bond character. - CORRECT ANSWER-charged.

Which of the following describes the entire three-dimensional structure of a single
polypeptide?
Tertiary structure
Quaternary structure
Primary structure
Secondary structure - CORRECT ANSWER-Tertiary structure

Which of the following amino acid residues form hydrogen bonds with Ala residues
located in an alpha-helix?
-Polar residues involved in the stabilization of tertiary structure.
-Residues located within the same -helix.
-Residues in a neighbouring -helix.
-None, because Ala is unable to form hydrogen bonds. - CORRECT ANSWER-
Residues located within the same -helix.

A domain is:
-a folded segment of polypeptide with -a separate hydrophobic core.
-an -helix, β-sheet or irregular secondary structure.
-the same as a protein's tertiary structure.
-always a motif. - CORRECT ANSWER-a folded segment of polypeptide with -a
separate hydrophobic core.

Which level of protein structure is defined as "the hydrogen bonded arrangement of the
polypeptide backbone"?
Which level of protein structure is defined as "the hydrogen bonded arrangement of the
polypeptide backbone"?
Secondary
Tertiary
Quaternary
Primary - CORRECT ANSWER-Secondary

Where are irregular secondary structures (loops) generally found in soluble globular
proteins and why?
-On the surface so that they can interact with the solvent.

, -On the surface because they are less compact.
-In the core of the protein so that they can interact with hydrophobic groups.
-In the core of the protein because they connect β-strands and -helices. - CORRECT
ANSWER-On the surface so that they can interact with the solvent.

Which of the following statements about quaternary structure is TRUE?
-Quaternary structure is defined as the 3D structure of proteins with four subunits.
-Quaternary structure requires covalent interactions between polypeptide chains.
-Quaternary structure is stabilized by the same types of noncovalent interactions as
tertiary structure.
-Quaternary structure exists only in proteins containing prosthetic groups. - CORRECT
ANSWER-Quaternary structure is stabilized by the same types of noncovalent
interactions as tertiary structure.

Which of the following series of amino acids is most likely to be buried in the center of a
water-soluble globular protein?
Pro, Gln, His
Gly, Asn, Ser
Glu, Asp, Lys
Ala, Leu, Phe - CORRECT ANSWER-Ala, Leu, Phe

Which of the following statements about peptide bonds is FALSE?
-Water is released when a peptide bond is formed.
-The peptide bond exhibits partial double bond character
-The peptide bond has restricted rotation around the bond between the carbonyl carbon
and C.
-The peptide bond is planar. - CORRECT ANSWER-The peptide bond has restricted
rotation around the bond between the carbonyl carbon and C.

Which one of the following sequences of five amino acids would most likely be located
in the interior of a water soluble globular protein?
Tyr-Phe-Glu-Asn-Leu
Met-Phe-Pro-Ile-Leu
Glu-Asn-Ser-Thr-Gln
Val-Ala-Val-Glu-Val - CORRECT ANSWER-Met-Phe-Pro-Ile-Leu

Compare the -helix with the structure of double-stranded DNA. Which statement is
TRUE for both structures?
-The backbones are on the outside of the helix.
-The hydrogen bonds are perpendicular to the axis of the helix.
-Hydrogen bonds are the primary determinant of stability.
-The helices are right handed. - CORRECT ANSWER-The helices are right handed

Which one of the following statements about the β-sheet is FALSE?
-The side chains in a β-sheet alternate between the two sides of the sheet.
-The β-sheet is a type of regular secondary structure.