Question 1

Loops and turns in proteins are

Accepted Answer

A) regions that let a polypeptide chain fold back on itself. 
B) stretches of non-repeating three dimensional structures in proteins. 
C) regions causing direction change in the polypeptide backbone. 
D) All of the above. 
A) regions that let a polypeptide chain fold back on itself. 
B) stretches of non-repeating three dimensional structures in proteins. 
C) regions causing direction change in the polypeptide backbone. 
D) All of the above.

Question 2

Protein folding can be followed in the laboratory by measuring

Accepted Answer

A) viscosity. 
B) electrophoretic mobility and gel filtration. 
C) UV absorption and light rotation. 
D) A,B,and C above. 
E) A and C above. 
A) viscosity. 
B) electrophoretic mobility and gel filtration. 
C) UV absorption and light rotation. 
D) A,B,and C above. 
E) A and C above.

Question 3

Proline is the least common amino acid in α-helices due to its inability to fully participate in intrahelical hydrogen bonding.

Accepted Answer

A) True 
 B)False

Question 4

________ is a technique used to analyze the macromolecular structure of proteins in solution.

Accepted Answer

A) X-ray crystallography 
B) SDS-PAGE 
C) Affinity chromatography 
D) NMR 
A) X-ray crystallography 
B) SDS-PAGE 
C) Affinity chromatography 
D) NMR

Question 5

Which represents the backbone of a protein? Note: R = amino acid side chain
N = nitrogen
Cα = alpha carbon
C = carbonyl carbon

Accepted Answer

A) R1R2R3R4R5. 
B) Repeating units of N-C. 
C) Repeating units of N-Cα-C. 
D) Repeating units of Cα-C. 
A) R1R2R3R4R5. 
B) Repeating units of N-C. 
C) Repeating units of N-Cα-C. 
D) Repeating units of Cα-C.

Question 6

Chaotropic agents denature by disrupting stabilizing hydrophobic interactions,while detergents denature by penetrating and disrupting hydrophilic interactions.

Accepted Answer

A) True 
 B)False

Question 7

Proteins with very high Tm values are generally stable at

Accepted Answer

A) room temperature (21°
C) . 
B) 50° to 60°C. 
C) temperatures below 50°C. 
D) temperatures above 60°C. 
E) All of the above. 
A) room temperature (21°
C) . 
B) 50° to 60°C. 
C) temperatures below 50°C. 
D) temperatures above 60°C. 
E) All of the above.

Question 8

Using simple computer algorithms biochemists can easily predict the tertiary structure of a protein from its sequence.

Accepted Answer

A) True 
 B)False

Question 9

Enzymes implicated in several human hereditary diseases are similar to ones that regulate flowering in Arabidopsis.These enzymes are

Accepted Answer

A) peptidyl cis isomerases. 
B) proline isomerase. 
C) prolyl cis/trans isomerase. 
D) isomerase hydrolase. 
A) peptidyl cis isomerases. 
B) proline isomerase. 
C) prolyl cis/trans isomerase. 
D) isomerase hydrolase.

Question 10

Protein subunits in a multisubunit protein are held to each other primarily by

Accepted Answer

A) covalent bonds. 
B) hydrophobic interactions exclusively. 
C) both strong and weak interactions. 
D) hydrophobic and other weak interactions. 
E) All of the above. 
A) covalent bonds. 
B) hydrophobic interactions exclusively. 
C) both strong and weak interactions. 
D) hydrophobic and other weak interactions. 
E) All of the above.

Question 11

For each term select the description that best describes its contribution to the structure of collagen.
-Allysine

Accepted Answer

A) Forms covalent cross links 
B) Makes the protein rigid 
C) Required for hydroxylation 
D) Allows tightly wound helix formation 
E) Has H bonds which help stabilize the protein 
A) Forms covalent cross links 
B) Makes the protein rigid 
C) Required for hydroxylation 
D) Allows tightly wound helix formation 
E) Has H bonds which help stabilize the protein

Question 12

Chaperones are proteins which prevent incorrect folding of proteins as well as preventing some proteins from aggregating.

Accepted Answer

A) True 
 B)False

Question 13

Which statement is false about the determination of protein structures?

Accepted Answer

A) NMR can generate sets of structures which may represent protein fluctuations. 
B) The structures found by NMR and X-ray crystallography are usually very different. 
C) It is often difficult to produce quality protein crystals for X-ray analysis. 
D) NMR spectroscopy exposes protein solutions to a magnetic field. 
A) NMR can generate sets of structures which may represent protein fluctuations. 
B) The structures found by NMR and X-ray crystallography are usually very different. 
C) It is often difficult to produce quality protein crystals for X-ray analysis. 
D) NMR spectroscopy exposes protein solutions to a magnetic field.

Question 14

Match each level of organization with a description.
-Quaternary structure

Accepted Answer

A) Specific order of amino acids 
B) Multiple subunits are present 
C) Overall shape of a protein 
D) Repeated pattern of folding 
A) Specific order of amino acids 
B) Multiple subunits are present 
C) Overall shape of a protein 
D) Repeated pattern of folding

Question 15

Hemoglobin is

Accepted Answer

A) a tetramer of 4 myoglobin proteins. 
B) a tetramer of four globin chains and one heme prosthetic group. 
C) a dimer of subunits each with two distinct protein chains (alpha and beta). 
D) a dimer of subunits each with two myoglobin proteins. 
E) an erythrocyte. 
A) a tetramer of 4 myoglobin proteins. 
B) a tetramer of four globin chains and one heme prosthetic group. 
C) a dimer of subunits each with two distinct protein chains (alpha and beta). 
D) a dimer of subunits each with two myoglobin proteins. 
E) an erythrocyte.

Question 16

The trans configuration of most peptide groups is adopted in cells because it

Accepted Answer

A) is the only one available. 
B) minimizes steric hindrance of R groups. 
C) is favored in protein synthesis. 
D) Both B and C. 
E) All of the above. 
A) is the only one available. 
B) minimizes steric hindrance of R groups. 
C) is favored in protein synthesis. 
D) Both B and C. 
E) All of the above.

Question 17

Cooperative binding and allosterism of hemoglobin allow oxygen to be unloaded at low partial pressures of oxygen in the tissues.

Accepted Answer

A) True 
 B)False

Question 18

Which is not true about β-sheets?

Accepted Answer

A) The side-chains of all amino acids point to the same side of the sheet. 
B) The polypeptide chains in the sheet are nearly fully extended. 
C) The range of allowed phi and psi angles is broader than for those in the α-helix. 
D) In antiparallel sheets the hydrogen bonds between adjacent strands are nearly perpendicular to the backbones of the strands. 
A) The side-chains of all amino acids point to the same side of the sheet. 
B) The polypeptide chains in the sheet are nearly fully extended. 
C) The range of allowed phi and psi angles is broader than for those in the α-helix. 
D) In antiparallel sheets the hydrogen bonds between adjacent strands are nearly perpendicular to the backbones of the strands.

Question 19

Proline is not often found in α-helices of proteins because it

Accepted Answer

A) has a small,uncharged side chain. 
B) has a very bulky side chain. 
C) lacks a hydrogen atom on its amide nitrogen. 
D) interacts with adjacent amino acids. 
A) has a small,uncharged side chain. 
B) has a very bulky side chain. 
C) lacks a hydrogen atom on its amide nitrogen. 
D) interacts with adjacent amino acids.

Question 20

Which factor does not help to explain why many proteins exhibit quaternary structure?

Accepted Answer

A) Oligomers are usually more stable than the free monomers. 
B) Active sites can be formed when the protein chains associate. 
C) The subunits always are able to maintain the same three-dimensional structure whether they are associated into an oligomer or not. 
D) Increased efficiency by the sharing of the same subunit with the same function among different proteins. 
A) Oligomers are usually more stable than the free monomers. 
B) Active sites can be formed when the protein chains associate. 
C) The subunits always are able to maintain the same three-dimensional structure whether they are associated into an oligomer or not. 
D) Increased efficiency by the sharing of the same subunit with the same function among different proteins.

Exam 4: Proteins: Three-Dimensional Structure and Function

Loops and turns in proteins are

Protein folding can be followed in the laboratory by measuring

Proline is the least common amino acid in α-helices due to its inability to fully participate in intrahelical hydrogen bonding.

________ is a technique used to analyze the macromolecular structure of proteins in solution.

Which represents the backbone of a protein? Note: R = amino acid side chain N = nitrogen Cα = alpha carbon C = carbonyl carbon

Chaotropic agents denature by disrupting stabilizing hydrophobic interactions,while detergents denature by penetrating and disrupting hydrophilic interactions.

Proteins with very high Tm values are generally stable at

Using simple computer algorithms biochemists can easily predict the tertiary structure of a protein from its sequence.

Enzymes implicated in several human hereditary diseases are similar to ones that regulate flowering in Arabidopsis.These enzymes are

Protein subunits in a multisubunit protein are held to each other primarily by

For each term select the description that best describes its contribution to the structure of collagen. -Allysine

Chaperones are proteins which prevent incorrect folding of proteins as well as preventing some proteins from aggregating.

Which statement is false about the determination of protein structures?

Match each level of organization with a description. -Quaternary structure

Hemoglobin is

The trans configuration of most peptide groups is adopted in cells because it

Cooperative binding and allosterism of hemoglobin allow oxygen to be unloaded at low partial pressures of oxygen in the tissues.

Which is not true about β-sheets?

Proline is not often found in α-helices of proteins because it

Which factor does not help to explain why many proteins exhibit quaternary structure?

Introduction to Biochemistry

Water

Amino Acids and the Primary Structures of Proteins

Properties of Enzymes

Mechanisms of Enzymes

Coenzymes and Vitamins

Carbohydrates

Lipids and Membranes

Introduction to Metabolism

Glycolysis

Gluconeogenesis, the Pentose Phosphate Pathway, and Glycogen Metabolism

The Citric Acid Cycle

Electron Transport and Atp Synthesis

Photosynthesis

Lipid Metabolism

Amino Acid Metabolism

Nucleotide Metabolism

Nucleic Acids

DNA Replication, repair, and Recombination

Transcription and RNA Processing

Protein Synthesis

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