8. Is facilitated diffusion passive or active transport?

Facilitated diffusion is **passive transport**. **Explanation:** - **Passive Transport:** This type of transport does not require the cell to expend energy (ATP). Instead, substances move down their concentration gradient, from areas of higher concentration to lower concentration. - **Facilitated Diffusion:** It specifically refers to the movement of molecules across the cell membrane through **transport proteins** (such as channels or carriers). This method is used for substances that cannot easily diffuse through the lipid bilayer of the cell membrane on their own, like glucose or ions. Since facilitated diffusion relies on the existing concentration gradient and does not require additional energy input, it is classified as passive transport. **Key Points:** - No energy (ATP) required. - Moves substances down their concentration gradient. - Utilizes specific transport proteins to aid movement.