Correct option is D
Explanation:
Phospholipids do not freely diffuse from one leaflet of the bilayer to another. The movement of phospholipids between leaflets (known as flip-flop) occurs very slowly and typically requires the action of specific enzymes called flippases, floppases, or scramblases. The flip-flop movement is energetically unfavorable and therefore does not happen spontaneously. On the other hand, lateral diffusion (within the same leaflet) is a very rapid and spontaneous process.
Information Booster:
Lateral diffusion of lipid molecules occurs freely in the plane of the bilayer, and this is a key characteristic of membrane fluidity.
The ratio of the head group size to the fatty acyl chain length of phospholipids affects membrane curvature, with smaller head groups and more unsaturated fatty acid chains favoring curvature.
Rotation of individual lipid molecules along their long axis is rapid and contributes to membrane fluidity and flexibility.
The phospholipid bilayer allows free lateral movement of lipids within a leaflet, but flip-flop requires enzyme-mediated processes due to the energy barrier involved.
Additional Knowledge:
Lipid molecules can diffuse freely in the plane of the bilayer (option 1) is true and an essential feature of biological membranes, allowing for dynamic membrane organization and function.
The ratio of the size of head group to fatty acyl chain of phospholipids contributes to the curvature properties of lipid membranes (option 2) is accurate. This ratio determines the packing and the formation of membrane structures like micelles or bilayers.
Individual lipid molecules rapidly rotate along their long axis (option 3) is true, contributing to the overall flexibility of the membrane.
