Question 1

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

Accepted Answer

The amino acid sequence that makes up the protein

Question 2

Which type of interaction is primarily responsible for stabilizing the secondary structure of proteins such as alpha helices and beta sheets?

Accepted Answer

Hydrogen bonds between backbone atoms

Question 3

A mutation causes a hydrophobic residue in the core of a globular protein to be replaced by a charged residue. What is the most likely effect on protein stability?

Accepted Answer

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

Question 4

Which of the following statements about beta sheets is TRUE?

Accepted Answer

Beta sheets are stabilized by hydrogen bonds between adjacent beta strands.

Question 5

Which of the following is a key thermodynamic factor that drives protein folding by increasing entropy?

Accepted Answer

Burying hydrophobic side chains in the protein interior, releasing ordered water molecules

Question 6

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

Accepted Answer

The spatial arrangement of multiple polypeptide chains to form multisubunit complexes

Question 7

Which of the following is a characteristic feature of alpha-keratin that contributes to its structural role in hair and nails?

Accepted Answer

It forms a coiled-coil structure stabilized by hydrophobic interactions.

Question 8

A protein domain is best defined as:

Accepted Answer

A compact, independently folding unit within a protein, often with a specific function

Question 9

Which of the following modifications would most likely increase the stability of a protein under harsh environmental conditions?

Accepted Answer

Increasing the number of disulfide bonds

Question 10

Which of the following best explains why silk fibroin is both strong and flexible?

Accepted Answer

It contains close-packed beta sheets interrupted by compact folded regions.

Question 11

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

Accepted Answer

Actin

Question 12

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

$$D_2$$

Question 13

Which of the following statements about the entropy changes during protein folding is correct?

Accepted Answer

Folding decreases the conformational entropy of the polypeptide chain but increases the entropy of the solvent.

Question 14

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

Accepted Answer

Loss of conformational entropy

Question 15

Which of the following best describes the arrangement of side chains in an alpha helix?

Accepted Answer

Side chains radiate outward from the helix axis.

Question 16

Which of the following is a real-life example of a protein whose stability is greatly increased by disulfide bonds?

Accepted Answer

Bovine pancreatic trypsin inhibitor (BPTI)

Question 17

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

Accepted Answer

It refers to the overall three-dimensional arrangement of all atoms in a single polypeptide chain.

Question 18

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

Accepted Answer

DNA recognition, oligomerization, or cofactor binding

Question 19

Which of the following best explains why collagen is an effective matrix material in bone?

Accepted Answer

It forms a triple helix structure that provides tensile strength and a scaffold for mineral deposition.

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

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