$$\text{Fluidity} \propto \text{Temperature}$$

Question 1

Which type of lipid diffusion describes the movement of lipids within the same leaflet of a bilayer?

Accepted Answer

Lateral diffusion

Question 2

What is the primary reason why transverse (flip-flop) diffusion of lipids across a bilayer is much slower than lateral diffusion?

Accepted Answer

It is energetically unfavorable due to the hydrophobic core.

Question 3

Which enzyme catalyzes the movement of phospholipids from the outer leaflet to the inner leaflet of a membrane?

Accepted Answer

Flippase

Question 4

What is the effect of increasing the number of double bonds in fatty acid chains on the transition temperature ($$T_m) of a $$membrane?

Accepted Answer

It decreases $$T_m.$$

Question 5

Which of the following best describes the role of scramblase in biological membranes?

Accepted Answer

It catalyzes the randomization of phospholipids between both leaflets.

Question 6

A membrane sample has a higher transition temperature ($$T_m) $$than a reference sample. Which of the following is the most likely explanation?

Accepted Answer

The sample has longer fatty acid tails and less double bond content than the reference.

Question 7

Which of the following processes requires ATP hydrolysis?

Accepted Answer

Flippase-mediated transverse diffusion

Question 8

What is the effect of loose packing of fatty acid tails on membrane fluidity?

Accepted Answer

It increases membrane fluidity.

Question 9

Which of the following statements about membrane fluidity is correct?

Accepted Answer

Membrane fluidity is increased by shorter fatty acid tails and more double bonds.

Question 10

Which of the following would NOT increase the transition temperature ($$T_m) of a $$membrane?

Accepted Answer

Increase in the number of double bonds in fatty acid chains

Question 11

Which of the following best explains why biological membranes remain fluid at physiological temperatures?

Accepted Answer

Presence of cholesterol and unsaturated fatty acids

Question 12

What is the main function of floppase in membrane lipid movement?

Accepted Answer

Moves phospholipids from the inner leaflet to the outer leaflet

Question 13

Which equation best represents the relationship between membrane fluidity and temperature?

Accepted Answer

$$	ext{Fluidity} \propto 	ext{Temperature}$$

Question 14

Which of the following factors would decrease the fluidity of a lipid bilayer?

Accepted Answer

Increase in saturated fatty acid content

Question 15

A patient’s cell membranes are found to have unusually high transition temperatures. Which of the following is the most likely cause?

Accepted Answer

Long, saturated fatty acid tails

Question 16

Which of the following statements about the transition temperature ($$T_m) of a $$membrane is TRUE?

Accepted Answer

$$T_m$$ increases with longer fatty acid tails and fewer double bonds.

Question 17

Which process is most likely to be catalyzed by an enzyme in the membrane?

Accepted Answer

Transverse (flip-flop) diffusion

Question 18

Which of the following is a consequence of increased membrane fluidity?

Accepted Answer

Increased lateral diffusion of lipids

Question 19

Which of the following best describes the effect of cholesterol on membrane fluidity at physiological temperatures?

Accepted Answer

Cholesterol increases membrane fluidity at low temperatures and decreases it at high temperatures.

Question 20

Which of the following is NOT a factor that affects the transition temperature ($$T_m) of a $$lipid bilayer?

Accepted Answer

Presence of membrane proteins

Physical Properties of Biological Membranes: Lipid Diffusion and Membrane Fluidity

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