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 .