Question 1

Which of the following best describes an integral membrane protein?

Accepted Answer

A protein that is embedded within the membrane and interacts extensively with the hydrophobic core.

Question 2

Which amino acid is most likely to be found in the transmembrane region of an integral membrane protein?

Accepted Answer

Leucine

Question 3

Integral membrane proteins are most commonly associated with which type of secondary structure when spanning the membrane?

Accepted Answer

$\alpha$-helix

Question 4

Which of the following statements about integral membrane proteins is NOT correct?

Accepted Answer

They can be released from the membrane by slightly changing the ionic strength of the solution.

Question 5

Which of the following best explains why $\beta$-barrel motifs are commonly found in porins of bacterial outer membranes?

Accepted Answer

They provide a hydrophilic channel through a hydrophobic environment.

Question 6

In the hydrophobic environment of a membrane, the $\alpha$-helix of a protein that spans the membrane will most likely have which type of amino acids facing the lipid tails?

Accepted Answer

Non-polar / Hydrophobic

Question 7

Which of the following is a key feature that distinguishes integral membrane proteins from peripheral membrane proteins?

Accepted Answer

Integral proteins span or are embedded in the membrane, while peripheral proteins are loosely attached to the membrane surface.

Question 8

A scientist isolates a protein from the mitochondrial membrane that forms a channel allowing ions to pass. Which structural motif is most likely present in this protein?

Accepted Answer

$\beta$-barrel

Question 9

Which of the following experimental treatments would most likely release a peripheral membrane protein from the membrane?

Accepted Answer

Changing the pH or ionic strength of the solution

Question 10

Which of the following best describes the orientation of hydrophobic and hydrophilic regions in an integral membrane protein?

Accepted Answer

Hydrophobic regions interact with the lipid bilayer, hydrophilic regions face the aqueous environment.

Question 11

Which of the following is a real-life example of a protein that utilizes a $\beta$-barrel motif to function as a channel in a biological membrane?

Accepted Answer

Porin

Question 12

A mutation causes a normally hydrophobic amino acid in the transmembrane region of a protein to be replaced by a charged amino acid. What is the most likely effect on the protein?

Accepted Answer

The protein may be destabilized and mislocalized due to unfavorable interactions with the lipid bilayer.

Integral Membrane Proteins: Structure, Properties, and Motifs

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