Particles move through the cell membrane from an area of higher concentration to lower concentration without the use of energy
Passive transport
Also described as movement along the concentration gradient
Types of passive transport
Diffusion
Osmosis
Facilitated diffusion
Diffusion
1. Particles move from an area of high concentration to low concentration
2. Continues until both sides have about equal numbers of particles
3. Achieves a state of equilibrium
Osmosis
Diffusion of water molecules through the cell membrane
Osmosis
1. Water moves freely from its area of high concentration to low concentration
2. Until equilibrium is reached, with the same proportion of water to solute particles on both sides
Facilitated diffusion
Molecules diffuse through specialized protein channels in the cell membrane
Facilitated diffusion
Allows particles a bit larger than those that can seep through the cell membrane's phospholipid layers to move in or out of the cell along the concentration gradient
Passive transport is a natural process that doesn't require the cell to expend any energy
