Here's why:

* Passive transport: Movement of substances across a cell membrane without requiring the cell to expend energy.

* Simple diffusion: The movement of a substance from an area of high concentration to an area of low concentration, driven by the concentration gradient.

In the context of food particles, small molecules like water, oxygen, and carbon dioxide can pass through the cell membrane via simple diffusion. This movement doesn't require the cell to use energy because it relies on the natural tendency of molecules to move from areas of high concentration to areas of low concentration.

Let me know if you have any other questions about cell transport!