Q: Which of the following statements about $$eta-$$sheets is correct?

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

Q: Which of the following is a characteristic feature of the $$eta-$$sheet structure in silk fibroin?

It is composed of $$eta-$$sheets that are extensively close-packed but interrupted by compact folded regions for elasticity.

Question 1

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

Accepted Answer

The spatial arrangement of the secondary structural elements in the polypeptide chain.

Question 2

A mutation causes a hydrophobic amino acid in the core of a globular protein to be replaced by a hydrophilic one. Which of the following is the most likely consequence?

Accepted Answer

The protein will likely misfold or become less stable due to disruption of the hydrophobic core.

Question 3

Which of the following interactions is NOT a major contributor to the stabilization of protein tertiary structure?

Accepted Answer

Covalent bonds between peptide backbones (excluding disulfide bonds).

Question 4

Which of the following statements about $$eta-$$sheets is correct?

Accepted Answer

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

Question 5

A protein is found to have three 2-fold axes of symmetry in its quaternary structure. Which symmetry group does it most likely belong to?

Accepted Answer

$$D_3$$

Question 6

Which of the following best explains the 'hydrophobic effect' in protein folding?

Accepted Answer

Hydrophobic side chains cluster in the protein interior, releasing ordered water molecules and increasing solvent entropy.

Question 7

Which of the following is a characteristic feature of the $$eta-$$sheet structure in silk fibroin?

Accepted Answer

It is composed of $$eta-$$sheets that are extensively close-packed but interrupted by compact folded regions for elasticity.

Question 8

Which of the following statements about protein domains is TRUE?

Accepted Answer

A typical protein domain is about 200 amino acids and can fold independently.

Question 9

Which of the following is a real-world example of a protein with a coiled-coil structure stabilized by hydrophobic interactions every four residues?

Accepted Answer

Keratin

Question 10

A researcher is studying a protein that requires a metal ion to maintain its structure. What is the most likely effect of removing the ion?

Accepted Answer

The protein will lose stability and may unfold.

Question 11

Which of the following best describes the arrangement of side chains in an $$eta-$$sheet?

Accepted Answer

Neighboring side chains are located on opposite faces of the sheet.

Question 12

Which of the following is a major thermodynamic factor that opposes protein folding?

Accepted Answer

Unfavorable loss of conformational entropy

Question 13

Which of the following is a correct statement about quaternary structure symmetry in proteins?

Accepted Answer

Helical symmetry allows for indefinite growth in length, as seen in actin and tobacco mosaic virus.

Question 14

Which of the following is a key feature of collagen structure?

Accepted Answer

It is a triple helix composed of three polypeptide chains.

Question 15

A protein is found to have a quaternary structure with one 4-fold axis and two 2-fold axes. Which symmetry group does it belong to?

Accepted Answer

$$D_4$$

Question 16

Which of the following is a real-life consequence of disulfide bond formation in proteins?

Accepted Answer

Disulfide bonds greatly increase protein stability, as seen in bovine pancreatic trypsin inhibitor.

Question 17

Which of the following best explains why the folded state of a protein is entropically unfavorable?

Accepted Answer

The folded state has only a few closely related conformations, resulting in lower entropy.

Question 18

A patient has a genetic disorder that prevents the formation of disulfide bonds in certain proteins. Which of the following symptoms might you expect?

Accepted Answer

Decreased stability of proteins exposed to oxidizing environments.

Question 19

Which of the following is a correct statement about the arrangement of $$eta-$$strands in a $$eta-$$sheet?

Accepted Answer

$$eta-$$strands in a sheet can be either parallel or antiparallel.

Question 20

Which of the following is a plausible effect of mutating a residue involved in a salt bridge (ionic bond) in the core of a globular protein?

Accepted Answer

The protein may lose stability due to loss of favorable charge-charge interactions.

Chapter 6: The Three-Dimensional Structure of Proteins – Study Notes

Study Guide - Practice Questions

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