1. Osmosis
Recall that osmosis specifically refers to water specifically moving through a membrane in and out. In this case, water is moving out of cells through the cell membrane into the water.
2. Diffusion
Diffusion is the movement of molecules according to a concentration gradient. Because of this, diffusion is a form of passive transport because it does not require energy. In this case, oxygen is moving freely from the lungs into the bloodstream. This process does not take energy, and because oxygen is a small, non charged molecule, it can diffuse freely, therefore the process is diffusion.
3. Active Transport
The sodium pump is a prime example of active transport. Remember that when pumps are involved, it essentially means whatever is moving cannot move by itself, but rather needs force behind it, which is provided by the pump. Because sodium cannot simply move out of a nerve cell, this is a form of active transport.
Hope this is helpful!
