Final answer:
The three main kinds of passive transport, all of which involve movement without cellular energy, are diffusion, osmosis, and facilitated diffusion.
Step-by-step explanation:
Passive transport is a critical biological process where small molecules or ions move across the cell membrane without the use of cellular energy. The three types of passive transport are:
- Diffusion, which is the random movement of particles from an area of high concentration to an area of low concentration until equilibrium is reached.
- Osmosis, a specific type of diffusion exclusive to water molecules. Water moves through a semipermeable membrane from a less concentrated solution into a more concentrated one to balance solute concentrations on both sides of the membrane.
- Facilitated diffusion, where specific transport proteins help move substances across the cell membrane. These substances often include ions or molecules that are too large or too polar to pass through the membrane by simple diffusion.
This overview does not require energy input by the cell, distinguishing it from active transport mechanisms, like pump transport, which does require energy usually in the form of ATP.