Ask a question

How can i tell if a cell is iso/hypo/hypertonic based on the number of molecules?

in my animal vet science class we are studying cells. we are doing a lab to determine if a cell is isotonic, hypertonic, or hypotonic. We are using an online software which is very confusing. It has me putting 10 solute and 10 water molecules inside of the cell and 20 water molecules outside of the cell. The question is "Describe whether the cell is isotonic, hypotonic, or hypertonic. explain.". My original answer is the cell is hypotonic because most of the solute molecules are inside of the but my friend disagrees with me and says the cell is isotonic. Can you shed some light?

1 Answer by Expert Tutors

Tutors, sign in to answer this question.
Nick O. | UCLA M.S. Biology| DAT Tutor| Professional| Patient |Effective |UCLA M.S. Biology| DAT Tutor| Profession...
5.0 5.0 (8 lesson ratings) (8)
If you think about it.. you are adding highly concentrated solute solution inside the cell and exposing it an environment lacking solutes (20 water molecules outside).
This means that water from outside the cell will want to go into to the cell as the cell is HYPERtonic to the surround HYPOtonic environment.
Only if both the cell and outside environment have the same solute concentrations will the cell be isotonic with its environment.
Hope that helps and let me know if you need anymore help!


So if the cell had 5 solute and 15 water molecules in and out of the cell, it would be isotonic? 
Yes, assuming we are disregarding any other potential sources of solutes.
Question. If the environment is 50% solvent and 50%solute and the cell is 75%solvent and 25%solute, will it make the solution hypertonic? Would the cell be hypotonic since the solute is much low in concentration then of the solvent. Thank u.