Question 1

Which level of protein structure is primarily responsible for the sequence of amino acids in a polypeptide chain?

Accepted Answer

Primary structure

Question 2

In an $$\alpha-$$helix, how are the side chains of amino acids oriented?

Accepted Answer

They radiate away from the helical axis

Question 3

Which of the following best describes the stabilization of $$\beta-$$sheets in proteins?

Accepted Answer

Hydrogen bonds between adjacent $$\beta-$$strands

Question 4

What is the main difference between parallel and antiparallel $$\beta-$$sheets?

Accepted Answer

Parallel sheets have both strands running N to C; antiparallel have one strand N to C and the other C to N

Question 5

Which fibrous protein is characterized by a coiled-coil structure and repeats of large hydrophobic residues every four positions?

Accepted Answer

Keratin

Question 6

What structural feature allows silk fibroin to be both strong and somewhat elastic?

Accepted Answer

Close-packed $$\beta-$$sheets interrupted by compact folded regions

Question 7

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

Accepted Answer

Loss of conformational entropy

Question 8

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 9

Disulfide bonds in proteins primarily serve to:

Accepted Answer

Increase protein stability

Question 10

A protein domain is typically defined as:

Accepted Answer

A region of ~200 amino acids that folds independently and often has a specific function

Question 11

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

Accepted Answer

Actin

Question 12

What type of symmetry is displayed by the tetrameric enzyme phosphofructokinase?

Accepted Answer

$$D_2$$ symmetry

Question 13

Which factor does NOT contribute to the stability of a folded protein?

Accepted Answer

Loss of conformational entropy

Question 14

In the context of protein folding, what is the 'hydrophobic effect'?

Accepted Answer

The clustering of hydrophobic side chains in the protein interior, releasing ordered water molecules

Question 15

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 16

Which protein is an example of a matrix material in bone, providing a scaffold for mineral precipitation?

Accepted Answer

Collagen

Question 17

Which of the following is a plausible consequence of a mutation that disrupts hydrogen bonding in the $$\alpha-$$helix of a protein?

Accepted Answer

Loss of helical structure and possible protein misfolding

Question 18

Which statement about $$\beta-$$sheets is correct?

Accepted Answer

Side chains alternate sides of the sheet

Question 19

A protein with $$C_2$$ symmetry is most likely to:

Accepted Answer

Have twofold symmetry about a perpendicular axis

Question 20

Which of the following is NOT a characteristic of globular proteins?

Accepted Answer

They are elongated molecules with well-defined secondary structures

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

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