Question

Explain how FRAP confirms the fluid mosaic model of membrane structure

Answer 1

The fluid mosaic model of a membrane structure states that the plasma membrane has a mosaic-like structure meaning that a variety of molecules like proteins, carbohydrates etc. float on the surface of the lipid molecules. These lipid molecules are capable of diffusing laterally, thus giving the membrane a fluid-like nature.

Fluorescence Recovery After Photobleaching (FRAP) is a techinique which uses fluorescently labelled probes to detect the movement of these surface proteins on the plasma membrane following photobleaching.

Fluorescently labelled probes againsts membrane proteins are used. Then, an area on the membrane is exposed to high intensity laser light to bleach the labelled molecules. This is followed by the use of a low intensity fluoroscent light to track the recovery of fluorescene in the bleached area. If the membrane indeed possesses a fluid like nature, teh bleached area will show recovery of fluorescence as a result of lateral diffusion of lipid molecules.