Passive Transport
Passive transport does not need energy to transport. The four main kinds of passive transport are diffusion, facilitated diffusion, filtration and osmosis. Proteins in the cell membrane act as
channels
to help move molecules along. There is also an in-between
transport process where very small molecules are able to cross a
semi-permeable.
Difussion
Diffusion is passive transport that occurs in nature.It is the movement of material from an area of high
concentration to an area with lower concentration until the concentration of the
solute is the same throughout and reaches equilibrium.
Facilitated Diffusion

Facilitated diffusion, also called carrier-mediated diffusion, is the movement of molecules across the cell membrane and special transport proteins that are enclosed within the cellular membrane. Many large molecules, such as glucose, are insoluble in lipids
and too large to fit through the membrane pores. Therefore, it will
bind with its specific carrier proteins, and the complex will then be
bonded to a receptor site and moved through the cellular membrane.
Filtration

Filtration is movement of water and solute molecules across the cell membrane due to hydrostatic pressure generated by the cardiovascular system.
Depending on the size of the membrane pores, only solutes of a certain
size may pass through it.
Osmosis

Osmosis is the diffusion of water moleculesacross a selectively permeable membrane. The movement of water
molecules through a partially permeable membrane from a solution of
high water potential to an area of low water potential. A cell with a
less negative water potential will draw in water but this depends on
other factors as well such as solute potential and pressure potential .