Q: What is the main stabilizing force in the close-packed $$b-$$sheet structure of silk fibroin?

Hydrogen bonds between adjacent $$b-$$strands

Q: Which of the following statements about $$b-$$sheets is TRUE?

Strands in $$b-$$sheets can be either parallel or antiparallel.

Question 1

Which level of protein structure is primarily responsible for the spatial arrangement of multiple polypeptide chains in a multisubunit complex?

Accepted Answer

Quaternary structure

Question 2

In an $$b-$$sheet, how are the side chains of neighboring amino acids oriented?

Accepted Answer

They alternate on opposite faces of the sheet.

Question 3

Which of the following interactions is NOT a favorable intramolecular enthalpic interaction that stabilizes protein folding?

Accepted Answer

Loss of conformational entropy

Question 4

A mutation replaces a hydrophobic residue in the interior of a globular protein with a charged residue. What is the most likely effect on protein stability?

Accepted Answer

Stability will decrease due to disruption of the hydrophobic effect.

Question 5

Which protein is characterized by a coiled-coil structure and is found in hair, fingernails, and intermediate filaments?

Accepted Answer

Keratin

Question 6

What is the main stabilizing force in the close-packed $$b-$$sheet structure of silk fibroin?

Accepted Answer

Hydrogen bonds between adjacent $$b-$$strands

Question 7

Which of the following best describes the tertiary structure of a protein?

Accepted Answer

The spatial arrangement of secondary structural elements in the polypeptide chain

Question 8

A protein domain is typically about how many amino acids and can fold independently?

Accepted Answer

200 amino acids

Question 9

Which of the following increases protein stability by forming covalent links between cysteine residues?

Accepted Answer

Disulfide bonds

Question 10

What is the effect of burying hydrophobic groups in the interior of a protein during folding?

Accepted Answer

It increases solvent entropy by releasing ordered water molecules.

Question 11

Which type of symmetry is displayed by the tetrameric enzyme phosphofructokinase, which has three 2-fold axes?

Accepted Answer

$$D_2$$ symmetry

Question 12

Which of the following is a real-world example of a protein with helical symmetry capable of indefinite growth in length?

Accepted Answer

Actin

Question 13

Which of the following statements about $$b-$$sheets is TRUE?

Accepted Answer

Strands in $$b-$$sheets can be either parallel or antiparallel.

Question 14

Which of the following is NOT a fibrous protein?

Accepted Answer

Ubiquitin

Question 15

Which factor contributes to the unfavorable loss of conformational entropy during protein folding?

Accepted Answer

Decrease in the number of possible conformations

Question 16

A protein binds a prosthetic group tightly. What is the most likely effect on the protein's stability?

Accepted Answer

Stability increases due to additional interactions.

Question 17

Which of the following best describes the arrangement of side chains in an $$b-$$helix?

Accepted Answer

Side chains radiate outward from the helix axis.

Question 18

Which of the following is a consequence of the hydrophobic effect in protein folding?

Accepted Answer

Ordered water molecules are released, increasing solvent entropy.

Question 19

Which of the following is a common function of a protein domain?

Accepted Answer

DNA recognition

Question 20

Which of the following is TRUE regarding the secondary structure of proteins?

Accepted Answer

It consists of local areas of repeating main chain structure such as $$b-$$helices and $$b-$$sheets.

The Three-Dimensional Structure of Proteins (Chapter 6 Study Notes)

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