Flashcards in Water Balance Deck (22)
Why do we need to regulate water content in the body?
The concentration of body fluids is usually different to that of the external environment
What happens if water uptake is less than water loss over time?
Not enough water, cells shrivel and die
What happens if water uptake is more than water loss over time?
Cells swell and eventually burst
What is osmosis?
Net movement of water across a selectively permeable membrane.
What is osmoregulation?
The process that balances the uptake and loss of water - under homeostatic control
What is passive movement?
Along a concentration gradient
What is active movement?
Against a concentration gradient
What influences the passive rate of movement?
Temperature, size of particles, electrical charge, concentration gradient
What is osmolarity?
measure of the osmotic pressure exerted by a solution across a perfect semi-permeable membrane compared to pure water
What is the calculation for osmolarity?
= (number of particles/molecules of solute) x (moles/litres)
How can we use osmolarity to compare two solutes?
When two solutes differ in osmolarity, one solution is hyperosmotic, with a greater concentration, and the other, with a lower concentration is hypo-osmotic
What does it mean if two solutions are iso-osmotic?
They have an equal osmolarity
What is tonicity?
The effect of a solution on cell volume, depends on concentration of non- penetrating solutes only
What are osmoconformers?
Iso-osmotic with the surroundings. All are marine animals. Because internal environment is same as external, there is no tendency to gain or lose water
What are osmoregulatory?
Osmolarity of body fluid regulated to within set range. Enables animals to live in environments that are uninhabitable for osmo-conformers, e.g. freshwater/terrestrial, or marine mammals to maintain different internal osmolarity to seawater.
What are limited osmoregulatory?
Have limited ability to regulate osmolarity of body fluid
Compared to the body fluids, what is the osmolarity difference in freshwater?
Freshwater is hypo-osmotic compared to the organism. Environment is high water concentration, low salt concentration
Compared to the body fluids, what is the osmolarity difference in seawater?
Seawater is hyper-osmotic compared to the organism. environment is low water concentration, high salt concentration
How do marine teleosts regulate water?
Are hypo-osmotic to the environment, salt is gained by diffusion and water is lost by osmosis. Small amounts of concentrated urine.
How do marine fish get rid of salt?
Na+/K+ ATPase pumps builds huge Na+ gradient within a chloride cell - Na is pumped out
Cl- transported using Na+ gradient (Cl-/Na+ symporters)
Cl- builds up and diffuses out
Na+ follows Cl- charge by sneaking through leaky tight cell junctions
How do freshwater teleosts regulate water?
Hyperosmotic to the environment. Salts are lost by diffusion, Salts and water gained in food, Water uptake by osmosis. Actively transport in salt, and produce large amounts of dilute urine