Which of the following is true about the sodium-potassium pump:

1. moves 3 Na⁺ out of the cell for each 2 K⁺ moved into the cell
2. moves 2 Na⁺ out of the cell for each 3 K⁺
   moved into the cell
3. moves 3 Na⁺ into each cell for each 2 K⁺ moved out of the cell
4. moves 2 Na⁺ into each cell for each 3 K⁺ moved out of the cell
5. none of these

Which is true for both saltwater and freshwater fish:

1. they are isotonic
2. they are hypertonic
3. they are hypotonic
4. they are hyperosmotic to each other

A red blood cell is placed in distilled water and starts to swell. Just before the cell lyses you take a sample of cytoplasm and analyze it. It is found to be what:

1. isotonic
2. hypertonic
3. hypotonic
4. hyposmotic
5. none of the above

Which of the following is not true for a freshwater fish in fresh water:

1. net diffusion of NaCl into the body at the gills
2. hyperosmotic body contents relative to the environment
3. active uptake of NaCl into the body at the gills
4. large amounts of dilute urine produced