The phrase “too large or too charged” is a helpful way to remember what kinds of molecules need to cross the cell membrane via a
n intermembrane protein, rather than by crossing directly through the phospholipid bilayer. Describe why some molecules can pass directly through the phospholipid bilayer, while those that are too large or too charged need to pass through a membrane protein.
Some molecules can pass directly through the phospholipid bilayer because of their small size which can easily pass through the small holes of phospholipid bilayer, while those that are too large or too charged need to pass through a membrane protein because membrane protein has a large holes through which large molecules can easily pass through the semi-permeable membrane of the cell by active or passive transport.
