Answer:
S.J. Singer and Garth L. Nicolson proposed the fluid mosaic model to describe the plasma membrane structure. They explained that the plasma membrane is a mosaic of carbohydrates, phospholipids, carbohydrates, and proteins.
This mosaic nature provides the fluid characteristic to the plasma membrane. This fluid behavior of the plasma membrane allows the movement of phospholipids and protein in the plasma membrane.
This movement of membrane components plays an important role in the transport of molecules across the cell.