Plasma Membrane Structure, Fluid Mosaic Model (2A) Practice Test

A toxin inserts into the outer leaflet of the plasma membrane and crosslinks neighboring phospholipid head groups without directly binding proteins. Shortly after exposure, FRAP of a labeled transmembrane protein shows reduced lateral recovery. Under the fluid mosaic model, which explanation is most consistent?

A cultured mammalian cell line is shifted from 37°C to 15°C for 30 minutes. Researchers then use fluorescence recovery after photobleaching (FRAP) on a GFP-tagged transmembrane receptor and observe slower lateral recovery at 15°C. The team proposes this is consistent with the fluid mosaic model of the plasma membrane. Which conclusion is most consistent with the model and the observation?