Question

Which of the following statements about lipids within a membrane is false?

a. They rotate rapidly around their long axes.

b. Enzymes called flippases generate membrane asymmetry.

c. They flip-flop readily from one monolayer to the other.

d. They rapidly exchange positions with one another within the plane of the membrane.

Answer 1

The correct answer will be:-

(c) They flip-flop readily from one monolayer to the other.

It is the false statement as flip-flop movement is intrinsically very slow. As they have polar regions so free-energy barriers to flip flop movement is larger.

So, lipid cannot readily flip flop from one monolayer to the other.

The other statements are true as :-

• Lipids rotates very rapidly around an axis which is perpendicular to the plane of the membrane i.e. long axis.
• Enzyme Flippase translocate phospholipids from one side of membrane to the other which causes asymmetric lipid distribution which results in lipids asymmetry.
• Exchange of lipid position with one another within the plane of the membrane is called as lateral movement which gives the membrane fluid structure. And it is rapid in nature.

So all the statements are true except (c).

Thus (c) is the correct answer.