The type of transport that does not require a protein to move molecules through the membrane is simple diffusion.
Here's a breakdown to help you understand:
1. **Simple diffusion**: In simple diffusion, molecules move across the cell membrane from an area of higher concentration to an area of lower concentration without the need for a protein carrier. This process occurs due to the natural tendency of molecules to spread out and reach equilibrium.
2. **Facilitated diffusion**: On the other hand, facilitated diffusion requires the assistance of specific protein carriers embedded in the cell membrane to help molecules move across the membrane. These proteins act as channels or carriers to facilitate the movement of molecules down their concentration gradient.
3. **Active transport**: Active transport, in contrast to both simple and facilitated diffusion, requires energy in the form of ATP (adenosine triphosphate) to move molecules against their concentration gradient. This process involves specific protein pumps that actively transport molecules across the membrane, even from an area of lower concentration to an area of higher concentration.
Therefore, in the context of your question, simple diffusion is the type of transport that does not require a protein to move molecules through the membrane.
