No, osmosis does not require a protein for water to move in and out of the cell. Osmosis is the process by which water molecules move across a selectively permeable membrane from an area of lower solute concentration to an area of higher solute concentration.
Water can pass through the cell membrane via simple diffusion, which does not involve any proteins. The cell membrane is composed of a phospholipid bilayer that allows water molecules to move directly through it due to their small size and polarity.
However, in certain cases, water can also move through specialized channels called aquaporins. These are indeed proteins that facilitate the rapid transport of water molecules, especially in cells that require fast water movement. But it is important to note that the presence of aquaporins is not a requirement for osmosis to occur. Water will still move across the membrane through passive diffusion if these proteins are not present.