By the cell membrane located on the outside of an animal or plant cell.
The membrane
A+ through nuclear pores
permeability
What you are considering when you are referring to how easily materials can pass through a membrane is how permeable the cell wall or membrane is.
The Cell Membrane
cell membrane
permeability
permeability
Mary Jane Mary Jane
the cell membrane
They pass through the cell walls and or membranes depending on wether or not its a plant or animal cell. Animal cells have only membranes. Plant cells have both.
proteins