Answer:
Water, carbon dioxide, and oxygen are among the few simple molecules that can cross the cell membrane by diffusion (or a type of diffusion known as osmosis ).
It is possible for large molecules to enter a cell by a process called endocytosis, where a small piece of the cell membrane wraps around the particle and is brought into the cell. If the particle is solid, endocytosis is also called phagocytosis. If fluid droplets are taken in, the processes is called pinocytosis.
