One way that materials pass through the cell membrane without requiring energy from the cell is through passive transport. Specifically, diffusion is a type of passive transport where molecules move from an area of high concentration to an area of low concentration, following the concentration gradient.

This movement doesn't require the cell to expend energy because the natural tendency of molecules is to spread out and distribute evenly. Examples of molecules that can pass through the membrane via diffusion include:

* Oxygen (O2): Cells need oxygen for respiration and it moves into the cell from the higher concentration in the surroundings.

* Carbon dioxide (CO2): A waste product of respiration, CO2 moves out of the cell following its concentration gradient.

* Small, uncharged molecules: These can pass through the cell membrane without the need for special transport proteins.

Let me know if you'd like more information about other types of passive transport!