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