Quiz on Protein Structure

The secondary structure of a protein refers to the extent and order of its α helices and β sheets.

• True

• False

Which of the following statements regarding protein domains is NOT true?

• Secondary structural elements of a domain generally pack so that a hydrophobic core is formed.

• A protein domain normally contains 50–200 residues.

• Protein domains are units of tertiary protein structure.

• Proteins are only comprised of one protein domain.

Most protein conformational changes involve breaking and reforming several covalent bonds along the polypeptide chain.

• True

• False

A conformational change in a molecule is:

• A change due to breaking covalent bonds

• A change due to forming new covalent bonds

• A change due to rotations of parts of the molecule about the covalent bonds

• A change due to adding new atoms to the molecule

The least restricted ϕ and ψ angles are found in polypeptides in which class of secondary structure?

• right-handed α helix

• β sheet

• left-handed α helix

• loop

Soluble proteins have mostly ________ sidechains on the inside and mostly ________ sidechains on the outside.

• acidic, basic

• hydrophobic, hydrophilic

• nonpolar, polar

• hydrophilic, hydrophobic

• polar, nonpolar

What is the rise along the helix axis per residue in an alpha helix?

• 1.5 Å

• 2.0 Å

• 1.0 Å

• 2.5 Å

How many residues are required to span a 70 Å membrane in an alpha helix?

• 47 residues

• 50 residues

• 40 residues

• 60 residues

What does the hydrophobicity index at each residue represent?

• The mean hydrophobicity value of the surrounding contiguous set of residues

• The maximum hydrophobicity value of a single residue

• The average hydrophilicity of the surrounding residues

• The total number of hydrophobic residues in a protein

How does the hydrophobicity index calculation differ for a new strain of bacteria with a thicker membrane?

• The window size should be decreased

• The window size should remain the same

• The window size should be increased

• The window size should be ignored