The passage of water from a region where it has higher water potential to a region where it has lower water potential through a selectively permiable membrane.
Understanding water potential:
Highest value for water potential, pure water, is zero.
Other values are negative. The higher the negativety the lower the water potential.
4.4 Active Transport
The movement of molercuels or ions into or of a cell from a region of lower concentration to a region of higher concentration using ATP and carrier proteins.
In Active transport ATP is used to:
- Directly move molecuels
- Individually move molecuels using a concentration gradient which has been set up by active transport. (co-transport)
How it differs from passive forms of transport:
- Metabolic energy in the form of ATP is required.
- Substances moved agaist a concentration gradient, from low to high.
- Carrier protein molecuels which act as pumps.
- Process is very selective with substance that is being transported.
4.4 Active Transport- Sodium Potassium Pump
In the sodium potassium pump sodium ionsare actively removed from the cell/organelle while potassium ions are actibvely removed from the surroundings.