Lecture 13 Flashcards
What is water balance?
How concentration of water is controlled within an animal.
Why is regulation required?
Concentration of body fluids is usually different to that of the external environments.
Define isotonic.
If at optimal water concentration, there will be no net movement in/out of cells.
Define hypotonic.
If the concentration of water is lower outside a cell, the cell will dry up.
Define hypertonic.
If the concentration of water is higher outside a cell, water will rush in and the cell may burst.
Define osmoregulation.
Process that balances uptake and loss of water (homeostatically controlled).
What factors increase passive movement of molecules.
Higher temperature, smaller particles, greater concentration gradient.
Define osmolarity.
Measure of osmotic pressure exerted by a solution across a semi-permeable membrane (that allows only water through) compared to pure water.
What is the osmolarity of pure water?
200
What is the osmotic condition of the cell and the solution when fluid is moving out of the cell?
The cell is hyperosmotic to the extracellular fluid.
The extracellular fluid is hypo-osmotic to the cell.
Define tonicity.
Effect of a solution on the cell membrane.
Depends on solutes and membrane permeability.
What happens to the cell when the solution is hypertonic?
There is net movement out of the cell (cells shrivel).
What happens to the cell when the solution is hypotonic?
There is net movement into the cell (cell bursts).
What happens when the solution is isotonic?
There is no net movement.
What are the 3 classes of organism to do with osmoregulation?
Osmocomformers, osmoregulators, limited osmoregulators.
