Chapter 6 Part 2 Test Questions – Flashcards

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

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

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

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

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 Val-Ala-Val-Glu-Val Glu-Asn-Ser-Thr-Gln

What ultimately determines the unique three dimensional structure of soluble globular proteins? The prosthetic groups. The exact number of disulfide bonds. The sequence of the amino acid residues. The number of subunits. The exact number of H-bonds.

Which of the following sequences of amino acids is most likely to be at the surface of a water-soluble globular protein? Glu-Asp-Lys Gly-Tyr-Val Pro-Phe-Thr Ile-Ser-Met Ala-Leu-Phe

Which of the following statements about quaternary structure is FALSE? Quaternary structure is defined as the arrangement of polypeptide backbones in proteins with four subunits. Quaternary structure is stabilized primarily by hydrophobic interactions. Quaternary structure exists only in proteins containing more than one polypeptide. Quaternary structure is fine-tuned by ion pairs, disulfide bonds, and hydrogen bonds.

Which of the following is TRUE about prosthetic groups? Prosthetic groups are bound and released by the protein as needed. Prosthetic groups are amino acids with additional reactivity. Prosthetic groups are inorganic. Prosthetic groups are an integral part of the three dimensional structure of the protein.

Which of the following statements about prosthetic groups is INCORRECT? Heme is an example of a prosthetic group. Prosthetic groups increase the inherent chemical reactivity of proteins. Prosthetic groups are not amino acids. Prosthetic groups form an integral part of the secondary structure of proteins

What is the major role played by prosthetic groups in proteins? They bind to the enzyme, participate in the catalytic reaction, and then leave the active site. They provide reactive groups not found in amino acid side chains. They provide flexibility in the enzyme structure. They maintain protein solubility. They are required to promote induced-fit by substrates.

Why does a decrease in pH alter/disrupt the tertiary structure of an enzyme? It deprotonates prosthetic groups. It promotes proteolytic cleavage of peptide bonds. It disrupts ion pairs/salt bridges. It reduces hydrophobic interactions. It reduces disulphide bonds.

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

The short amino acid sequence shown below occurs within the longer amino acid sequence of a large protein. This specific portion of the amino acid sequence adopts an -helical conformation. ............Ala-Val-Ala-Val-Ala-Val-Ala-Val-Ala-Val............... When the protein has adopted its tertiary conformation, which of the following hydrogen bonds are most likely to be formed by groups on the amino acid residues in this short segment? Hydrogen bonds with other residues in the same -helix. None, because Ala and Val side chains are unable to form hydrogen bonds. Hydrogen bonds with water molecules at the surface of the protein. Hydrogen bonds with residues in a neighbouring -helix.

What is the major factor that "drives" the folding of proteins into their tertiary structure? Formation of the maximum number of hydrophilic interactions. Placement of hydrophobic amino acid residues within the interior of the protein. Formation of the maximum number of ionic interactions. Placement of polar amino acid residues on the surface of the protein.

Which of the following statements about quaternary structure is TRUE? Quaternary structure requires covalent interactions between polypeptide chains. Quaternary structure exists in monomeric proteins. Quaternary structure is defined as the precise, 3-D arrangement of polypeptide backbones in proteins with more than one subunit. Quaternary structure is stabilized by the same types of noncovalent interactions as tertiary structure.

Which statement about the families of protein folding patterns is false? Folding patterns that are commonly found are those which are likely to tolerate substitutions, insertions, and deletions in the amino acid sequence. The number of folding patterns seems to be much smaller than the number of proteins. Proteins of similar primary structure tend to have similar tertiary structure. Proteins of similar tertiary structure tend to have a very similar primary structure.

Which of the following statements is true because of the hydrophobic effect? Charged polar residues R, H, K, E, and D are usually found on the surfaces of proteins. Nonpolar residues V, L, I, M, and F are found in the interior of proteins. Uncharged polar residues S, T, N, Q, and Y are usually found on the surface of proteins, but may also be found in the interior. The interior of proteins is packed very densely.

Which statement is not a consequence of the hydrophobic effect? Nonpolar side chains are buried in the interior of a protein. The folding of proteins is generally a favorable process. The entropy of water increases when proteins fold. Metal ions can function to stabilize folded proteins.

Which pairs of amino acid side chains could not interact in the interior of a protein by hydrogen bonding? Asp, Asn Ser, His Gln, Thr Ala, Lys

Which pair of amino acid side chains could form an ion pair? Glu, Gly Asp, Gln His, Asp Lys, Arg

In the experiment of Christian Anfinsen, which condition permitted Ribonuclease A to renature? Entry field with correct answer Exposure to high temperatures during renaturation. The use of 8 M urea to denature the protein. The presence of O2 at pH 8.0 during renaturation. The presence of 2-mercaptoethanol during denaturation

Which is NOT a conclusion drawn from the experiments of Christian Anfinsen about renaturation of Ribonuclease A? A protein's primary structure can determine its tertiary structure. A protein can fold spontaneously to its native structure without the presence of other factors. Proteins are marginally stable in solution. A protein can fold rapidly to its native structure.

Which of the following pairings of a supersecondary structure / motif and a statement describing it is INCORRECT: immunoglobulin fold: two B- a- B - a - B units that combine to form a dinucleotide-binding site. a-a motif: two successive antiparallel a -helices packed against each other with their axes slightly inclined. B - a -B motif: an a -helix connecting two parallel strands of a B-sheet. B-hairpin motif: two anti-parallel B-strands connected by a tight turn. B-barrels: B-sheets that are rolled-up to form a continuous, circular sheet, with the first strand adjacent to the last strand.

Which of the following statements about domains found in multi-domain proteins is false? They resemble small, globular proteins. They often have specialized functions. They contain 20-50 amino acids. They are often structurally independent.

Which of the following is not a requirement for the structural determination of a protein using two-dimensional (2D) NMR spectroscopic techniques such as NOESY? Known geometric constraints such as covalent bond distances and angles. A low molecular mass no greater than ~40 kD. The ability of the protein to crystallize. The protein's primary amino acid sequence.

Which statement about disulfide bonds is false? Disulfide bonds help stabilize extracellular proteins. Disulfide bonds are rare in intracellular proteins because the cytoplasm is a reducing environment. Disulfide bonds can occur between two different polypeptide chains. Disulfide bonds can occur between either Cys or Met residues. Disulfide bonds are not essential for stabilizing a folded protein. Can be reductively cleaved by 2-mercaptoethanol. Disulfide bonds can occur within a polypeptide chain.

Which treatment is least likely to cause a protein to denature? High concentrations of detergents like SDS. Extremes of pH. Temperatures approaching 100oC. High concentrations of salts. High concentrations of chaotropic agents like urea or the guanidinium ion.

Which pairs of amino acid side chains could interact in the interior of a protein only via van der Waals interactions? Entry field with correct answer Gln, His. Ser, Ser. Arg, Thr. Val, Leu

Which of the following is not a disease that is caused by protein misfolding? Bovine spongiform encephalopathy. Alzheimer's disease. Creutzfeldt-Jakob disease. Down's syndrome.