In active transport, the cell has to pay (often, in the form of ATP) to move molecules against their gradients. Learn more about the amazing protein machines that make this possible.
Ever wonder why plants wilt if you don't water them? Find out here, and learn more about the basic principles of probability that underlie movement of water and other molecules in biological systems.
Membranes_and_transport_skill_checks
Check your understanding of membrane structure, diffusion, osmosis, and transport!
Learn about the amazing and versatile barrier that surrounds all of your cells: the plasma membrane!
Sometimes it pays to go with the flow! Learn about passive transport mechanisms, in which molecules travel across the plasma membrane by moving down their concentration gradients (no energy expenditure required).
Macrophages (specialized immune cells) in your body can "eat" bacteria, pulling them into the cell and digesting them. Learn how they accomplish this feat, and how cells transport other large molecules across the plasma membrane.
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