A student prepared different salt water solutions in preparation for a tonicity experiment. The goal of the experiment is to find a salt concentration in which the cell can maintain homeostasis, meaning that the cell neither loses nor gains water. The table shows the salt concentration for each set up.

Question

Beaker Concentration (g/ml)
A 1.10
B 1.12
C 1.14
D ?

The student placed a cell with an internal salt concentration of 1.01 g/ml into each of the beakers. After testing with beakers A–C, and not getting accurate results, they decide to do the experiment one last time using beaker D.

How can the experiment be modified so that the cell maintains homeostasis?
A.Make the concentration of beaker D greater than 1.14 g/ml since the cell was taking in more water than it was losing with beakers A-C.
B.Make the concentration of beaker D less than 1.01 g/ml since the cell was taking in more water than it was losing with beakers A-C.
C.Make the concentration of beaker D 1.01 g/ml since the cell was losing more water than it was taking in with beakers A-C.
D.Make the concentration of beaker D between 1.10 g/ml and 1.14 g/ml since the cell was losing more water than it was taking in with beakers A-C.

Answer 1

In osmosis, cells will gain or lose water depending on the tonicity of the surrounding solution compared to their internal environment. Since the cell in question has an internal salt concentration of 1.01 g/ml, we need to consider the results from beakers A, B, and C to determine how to modify the concentration in beaker D for the cell to maintain homeostasis.

If the external salt concentration is greater than the internal concentration of 1.01 g/ml (as in the cases of beakers A at 1.10 g/ml, B at 1.12 g/ml, and C at 1.14 g/ml), the cell loses water to the environment, leading to a hypertonic environment.

Conversely, if the external concentration is less than 1.01 g/ml, the cell would take in water, leading to a hypotonic environment.

To achieve homeostasis, where the cell neither loses nor gains water, the concentration in beaker D should ideally be equal to the internal concentration of 1.01 g/ml.

Therefore, the best modification would be:

C. Make the concentration of beaker D 1.01 g/ml since the cell was losing more water than it was taking in with beakers A-C.

This concentration (1.01 g/ml) would create an isotonic solution, enabling the cell to maintain homeostasis.