The cell is taking in substances through membrane proteins, without any energy expenditure of its own. The substances naturally follow their concentration gradient. However, they must go through the protein channels, because they are too large to squeeze through the cell membrane. This process is called A) osmosis. B) endocytosis. C) active transport. D) facilitated diffusion.
This process is called Facilitated diffusion. because the protein channels must help the substance get into the cell based on fitting. It's important to regulating what comes in and goes out.
