UBCH Chapter 6 – Flashcards

Please match the correct term on the top with the appropriate structural feature of proteins listed on the bottom. 1) primary structure 2) secondary structure 3) tertiary structure 4) quaternary structure A) the interaction between two separate protein strands B) the sequence of AA C) small sections of organized protein structure, such as helices D) the overall fold of a single protein strand, such as the globulin fold A) 1:D; 2:C; 3:B; 4:A B) 1:C; 2:D; 3:A; 4:B C) 1:B; 2:C; 3:D; 4:A D) 1:B; 2:A; 3:D; 4:C

Match the following characteristics to α helices, β sheets, or both. 1) 5.4Å/turn A) α helices 2) antiparallel arrangement B) β sheets 3) large dipole moment C) both 4) extensive H-bonding network A) 1:A; 2:B; 3:A; 4:C B) 1:A; 2:C; 3:A; 4:B C) 1:A; 2:A; 3:C; 4:B D) 1:B; 2:B; 3:A; 4:A

A short 8-residue sequence of a polypeptide is determined to have φ angles ranging from -65 degrees to -80 degrees and ψ angles ranging from -40 degrees to -50 degrees. What conclusion can be drawn from this data? A) This segment is mostly β sheet. B) This segment has helical content. C) The sequence has no defined secondary structure. D) No conclusion can be drawn.

Which statements about β and γ turns are correct? 1) Their purpose is to reverse the direction of the polypeptide chain. 2) There are two types, I and II, which differ mainly in the conformation about the i+1 and i+2 residue amide bond. 3) They typically contain large, hydrophobic residues. 4) Their conformation is held in place through H bonds. Which statements about β and γ turns are correct? A) Only statements 1, 2, and 3 are correct. B) Only statements 2, 3, and 4 are correct. C) Statements 1, 2, and 4 are correct. D) All of the listed statements are correct.

Which of the following statements regarding the folding of proteins is NOT true? A) Salt bridges stabilize the fold. B) Hydrophobic residues pack together because the side chains are attracted to each other through weak Van der Waals interactions. C) Internal H bonds stabilize the fold. D) Van der Waals interactions have a stabilizing, cumulative effect.

Which of the following statements is NOT true? A) A prosthetic group is usually a small organic molecule required for activity by a protein. B) A cofactor usually refers to a metal ion required for activity by a protein. C) An intact protein, complete with its cofactor or metal ion, is known as a holoprotein. D) A protein stripped of its cofactor or metal ion is known as a holoprotein.

Which of the following statements about protein quaternary structure are correct? 1) It involves a complex of two or more proteins interacting with each other. 2) The subunits of the structure can be either identical or different. 3) The interactions between subunits can give rise to indefinite growth of polymeric complexes. 4) Most assemblies of protein subunits have one or more defined axis of rotation. A) Only statements 2, 3, and 4 are valid. B) Only statements 1, 2, and 3 are valid. C) Only statements 1, 3, and 4 are correct. D) All of the listed statements are correct.

The protein that makes up about a third of the total protein mass in animals is: A) α-keratin. B) hemoglobin. C) collagen. D) myoglobin. E) β-keratin.

Protein folding is a random process, whereby a vast number of possible conformations are tested to find the desired most stable state. A) True B) False

Which of the following statements regarding Anfinsen's denaturing experiments with ribonuclease A are valid? 1) Exposing the denatured protein to air oxidation and then dialysis to remove urea restored the protein to its original functionality. 2) Removing urea by dialysis and then allowing air oxidation of the denatured protein restored the protein to its original functionality. 3) Denaturing the protein with both urea and β-mercaptoethanol yielded an inactive protein. 4) Protein folding is determined by its primary sequence. A) Statements 1, 2, and 4 are valid. B) Statements 1, 2, and 4 are valid. C) Only statements 2, 3, and 4 are valid. D) All of the listed statements are valid.

D) β-sheet

B) β-helix

Proteins are polymers of _____. A) glycerol B) nucleotides C) CH2O units D) amino acids E) hydrocarbons

What type of bond joins the monomers in a protein's primary structure? A) ionic B) hydrophobic C) peptide D) S - S E) hydrogen

The secondary structure of a protein results from _____. A) hydrogen bonds B) hydrophobic interactions C) bonds between sulfur atoms D) peptide bonds E) ionic bonds

Tertiary structure is NOT directly dependent on _____. A) ionic bonds B) hydrophobic interactions C) hydrogen bonds D) peptide bonds E) bonds between sulfur atoms

A ________ plot describes which structures in a polypeptide are sterically possible and which are not based on the angles of rotation about the backbone Namide -Cα and Cα-Ccarbonyl bonds.

It has been found that in some of the α-helical regions of hemerythrin, about every third or fourth amino acid residue is a hydrophobic one. Suggest a structural reason for this finding. A) Suggest a structural reason for this finding. B) The hydrophobic residues share polar regions of the helix, forming a regular helical structure C) This order of residues stabilize turns and affects the angle of rotation of spiral turns. D) The four helices could be arranged so that to stabilize hydrophobic core.

What would be the effect of a mutation that placed a proline residue at point A in the structure? A) This would break the helix near the binding sites and Fe2 could not be bound, and the mutant protein would be nonfunctional. B) This would break the helix and form hairpin structures, that would make the mutant protein nonfunctional. C) This would break the helix near the Fe2 binding sites, and the mutant protein would change functions.

The amino acid side chain residues in an α helix point outwards away from the center of the helix. A) True B) False

Fibroin is a β-sheet protein, with a high proportion of glycine. A) True B) False

Tropocollagen is a double helix of two left-handed polypeptide chains. A) True B) False

Which of the following is CORRECT when considering the tertiary structure of globular proteins? A) The amino acid proline never occurs in a region where the polypeptide chain bends or turns. B) All parts of the proteins can be classified as helix, β sheet or turns. C) Hydrophobic residues are normally on the inside and hydrophilic residues are on the outside. D) β sheets cannot be twisted or wrapped into barrel structures. E) None of the above.

Proteins cannot self-assemble into a functional conformation after they have been denatured. A) True B) False

The folded conformation of proteins can be stabilized by the binding of a metal ion or cofactor. A) True B) False

Please match the correct term on the left with the appropriate structural feature of proteins listed on the right. 1) primary structure A) the interaction between two separate protein strands 2) secondary structure B) the sequence of AA 3) tertiary structure C) small sections of organized protein structure, such as helices 4) quaternary structure D) the overall fold of a single protein strand, such as the globulin fold Please match the correct term on the left with the appropriate structural feature of proteins listed on the right. A) 1:B; 2:C; 3:D; 4:A B) 1:B; 2:A; 3:D; 4:C C) 1:C; 2:D; 3:A; 4:B D) 1:D; 2:C; 3:B; 4:A

In considering protein secondary structure which of the following is INCORRECT? A) A network of main-chain hydrogen bonds connect β strands in a β sheet. B) The most common structures are the α helix and the β sheet. C) An α helix repeats after 18 residues and has 3.6 residues per turn. D) The β strands can be in either parallel or antiparallel configuration. E) The 310 helix is right-handed and often contains proline residues.

Proteins have an asymmetrical tertiary structure, while multisubunit proteins can exhibit several types of symmetry. A) True B) False