How do the cells in your body define their boundaries (and control what comes in or goes out)? As it turns out, cells have a sophisticated and flexible barrier, the plasma membrane, and a wide array of strategies for transporting molecules in and out. Learn more about what the membrane's made of and how different types of molecules move across it.
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.