Osmoregulation Lecture 3 Flashcards
Is urea and TMAO compatible osmolytes?
Seperatly, no they are not. However put together they behave as compatible osmolytes.
Nephrons:
The excretory tubules called nephrons are located in a specialized organ called the kidney.
In all nonmammallian vetebrates the kidney produces urine that is either
hyposmotic or isoosmotic to body fluids with the exception of some birds being able to rpoduce urine that is a littler hyperosmotic.
Do the kidneys in fish play a significant role in regulation of salts?
No because they cannot produce hyperosmotic pee.
What part of the fish does play a big role in excretion of salt?
The Gills! there are specialized cells in the gills called called chloride cells which actively transport Cl into the sea. Na and K are also actively transported to maintain balance.
How are sharks and sting rays different to the small fish in salt excretion?
The osmolarity of their body fluids is maintained not by excreting salt out but by increasing concentrations of Urea and TMAO. Excess salts are excreted in the kidney and by specialized glands called rectal salt glands near the anus.
How do freshwater fish maintain osmolarity?
They are hyperosmotic to their environment. The excrete large quantities of dilute urine to get rid of excess water. Salt is replaced by eating it in foods and the active transport of Na, K and Cl from the gills. Nitrogenous watse is excreted by the gills as ammonia.
How do amphibians get salt?
They obtain salt from the water through active transport across their skin.
How do reptiles conserve water?
The scales covering their body allow almost no water to be lost this way.
How do birds and and reptiles that live around sea water excrete salt?
Through specialized salt glands located in the head that remove salts from the blood by active transport. Excreted in a solution that is 2 or 3 times higher than the salt body fluids.
Marine osmoregulators (salt water fish) are what to their environment?
Hypo-osmotic
Therfore how do they get water?
Maintain water balance by drinking water!
Freshwater osmoregulators are what to their environment?
Hyper-osmotic.
Do fresh water fish drink water?
No! They do not need to!
In marine fish we have to pump ions out to account for the ions moving in with the water that they have to drink. What generates the membrane potential? What does the cause the inside of the chloride cell to become?
3 Na going out and 2 K going in creates a membrane potential. This causes the inside of the cell to become negative.
