Question

Ocean fish live in an extremely salty environment where there is a higher concentration of salts in their surroundings than inside their cells. This means that salt wants to enter the cells of ocean fishes.

How do ocean fish maintain homeostasis within their cells with regards to salt concentrations?

Answer 1

Chloride cells in the gills of marine fish produce an "enzyme", called gill Na+/K+ ATPase, that enables them to rid their plasma of excess salt, which builds up when they drink sea water. They use the enzyme to pump sodium out of their gills at the cost of energy.