Basis on the fluid mosaic model of the cell membrane, which type of molecule can move passively across the membrane, without the aid of proteins

The cell membrane is composed of a phospholipid bilayer. Because it is made of lipids, they are non-polar molecules. That means that other non-polar molecules can easily pass through. In addition to other non-polar molecules, small, uncharged molecules like water, glycerol, ethanol can also pass through without the use of channel or carrier proteins.