All cells take in nutrients and expel waste through the cell membrane. The cell membrane is selectively permeable, allowing some substances to pass through passively via diffusion, osmosis, or facilitated diffusion without using energy. Other substances require active transport using transport proteins and cellular energy to move against the concentration gradient into or out of the cell. There are two main types of active transport: endocytosis which surrounds and takes material into the cell, and exocytosis which expels material out of the cell.

1. Moving Cellular Materials

5. Three types of Passive Transport Passive Transport Diffusion Osmosis Facilitated Diffusion