Answer:
Fluorescence recovery after photobleaching.
Explanation:
The molecules can move inside and outside of the cell trough the semi permeable membrane. The molecules might require or do not require energy depending upon the concentration gradient.
The FRAP (fluorescence recovery after photobleaching) is the techniques used to identify the diffusion and lateral movement of molecules. This technique uses the fluorescence molecule and then the photobleaching of that particular molecule is directly proportional to the movement of molecule. The bleaching can be observed on the autoradiography.