4.3 Osmosis

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4.3 Osmosis

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. 

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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. 
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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. 

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