Passive transport includes diffusion and osmosis.
Molecules tend to move from crowded to less crowded in order to achieve a balance or to reach homeostasis. The cell membrane is selectively permeable which allows the movement of substances, especially oxygen, water, food molecules, carbon dioxide, and waste products, into or out of the cell. Movement occurs when there are unequal concentrations of a substance inside and outside of the cell. Print this page in Adobe Acrobat format. Visit the Utah State 7th Grade Integrated Science Core Curriculum Page .