Diffusion, osmosis and active transport

Diffusion - the net movement of molecules of a as or liquid from a high concentration to an area of low concentration

Factors that affect diffusion -  

• Temperature - the higher the temperature the more kinetic energy = more collisions = faster rate of diffusion
• Surface area - greater the surface area the more room for molecules to work upon = faster diffusion rate
• Diffusion pathway - diffusion effcient over short distances. Surfaces which are thin like the epithelium of the intestines = shorter distance to diffuse = faster diffusion rate
• Concentration gradient - the greater the difference = faster the rate of diffusion.   e.g. the blood is continually transporting products of digestion away from the intestine wall, ensuring large difference in conc = faster rater of diffusion

Facilitated Diffusion - diffusion which involves an intrinsic carrier protein 

• When a large molecule wants to gain entry into a cell through the cell membrane e.g. Glucose 
• For the molecule to pass thought it must be correct/specific shape
• If it is the correct complementary shape the carrier protein will release it onto the other side.

Speeds up with Kinetic Energy

 
Passive process but does not require energy from respiration

Osmosis - the net movement of water from a region of high water potential (  ) to low (  ) through a partially permable membrane 

High (  ) = a high concentration of water = much more movement = osmosis possible

Low (  ) = low concentration = little movement of water = osmosis likey to be low.

Affecting Water potential (  )

• By dissolving substance in the water
• MORE dissolved susbtances = the lower the water potential becomes ( Na+ , Cl- , Glucose)

Active Transport - movement of molecules against a concentration gradient from low to high using ATP energy and a carrier protein

Useful:- 

• for concentrating susbtances e.g  Salt Gland Marine Iguanas
• Taking up ions from the soil into plant root cells where there are more concentrated.