Question 1

Which of the following interactions is primarily responsible for stabilizing the tertiary structure of a protein by forming a nonpolar center in the interior of the molecule?

Accepted Answer

Hydrophobic interactions

Question 2

What type of bond forms between the sulfur atoms of two cysteine residues in a protein's tertiary structure?

Accepted Answer

Disulfide bond

Question 3

Which of the following best describes the quaternary structure of hemoglobin?

Accepted Answer

It consists of four polypeptide subunits held together by the same interactions as in tertiary structure.

Question 4

Which interaction would you expect between the R groups of phenylalanine and valine in a protein's tertiary structure?

Accepted Answer

Hydrophobic interaction

Question 5

A mutation in hemoglobin replaces a polar acidic glutamic acid with a nonpolar valine. What is the most likely consequence for the protein's structure and function?

Accepted Answer

Increased hydrophobic interactions leading to aggregation and sickle-shaped red blood cells

Question 6

Which of the following is NOT a stabilizing interaction found in the tertiary structure of proteins?

Accepted Answer

Peptide bonds between amino acids

Question 7

Which protein carries oxygen in muscle tissue and has a molar mass of approximately $$17\ 000$$?

Accepted Answer

Myoglobin

Question 8

Which of the following best explains why sickle-cell hemoglobin molecules form insoluble fibers?

Accepted Answer

Hydrophobic interactions between nonpolar valine residues cause the molecules to stick together.

Question 9

Which of the following statements about the tertiary structure of proteins is correct?

Accepted Answer

It is the overall three-dimensional shape formed by interactions between R groups of amino acids.

Question 10

Which of the following is a real-life consequence of sickle-cell anemia at the molecular level?

Accepted Answer

Red blood cells become crescent-shaped, reducing their ability to transport oxygen.

Question 11

Which of the following interactions would most likely occur between the R groups of lysine (a basic amino acid) and aspartic acid (an acidic amino acid) in a protein's tertiary structure?

Accepted Answer

Salt bridge

Question 12

Which structural level of a protein is directly affected when multiple polypeptide chains assemble into a functional protein complex?

Accepted Answer

Quaternary structure

Question 13

Which of the following best describes the difference between hemoglobin and myoglobin?

Accepted Answer

Hemoglobin carries four oxygen molecules, while myoglobin carries one.

Question 14

A protein's tertiary structure is disrupted by the addition of a reducing agent. Which interaction is most likely broken?

Accepted Answer

Disulfide bonds

Question 15

Which of the following is a correct sequence of protein structural levels from simplest to most complex?

Accepted Answer

Primary, secondary, tertiary, quaternary

Question 16

Which of the following interactions is most likely to occur on the exterior surface of a soluble protein in water?

Accepted Answer

Hydrophilic interactions

Question 17

Which of the following best explains why proteins with nonpolar R groups tend to fold with those groups on the inside of the molecule?

Accepted Answer

Nonpolar R groups are hydrophobic and are repelled by the aqueous environment.

Question 18

Which of the following is a direct result of the replacement of glutamic acid with valine in sickle-cell hemoglobin?

Accepted Answer

Formation of insoluble fibers that clog capillaries

Question 19

Which of the following is a covalent bond that stabilizes the tertiary structure of proteins?

Accepted Answer

Disulfide bond

Question 20

Which of the following is a real-world example of a disease caused by a single amino acid substitution in a protein?

Accepted Answer

Sickle-cell anemia

Proteins: Tertiary and Quaternary Structures (Amino Acids and Proteins)

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