How does the filamentous green algae Cladophora cells look under a microscope in an isotonic, hypotonic, and hypertonic solution?

Question

I need help in identifying how the algae cells looks like under a microscope in each situation.

Answer 1

This question is all about understanding diffusion and salt concentrations of the solutions. Remember that:

isotonic = similar salt concentration

hypotonic = lower salt concentration

hypertonic = higher salt concentration

In osmosis, water will selectively diffuse across the membrane of the algae in order make the concentration of salt out side of the cell equal to the concentration of salt inside the cell. In this type of diffusion water will always flow from the low salt area to the high salt area (this dilutes salt in the high concentration area and concentrates the low concentration area). So lets think about what will be happening in each solution:

isotonic = similar salt concentration = no diffusion

hypotonic = low concentration of salt is outside the cell = water flows into the cell

hypertonic = low concentration of salt is inside the cell = water flows out of the cell

Now you just have to think about what adding or removing water will do the algae. A good analogy is a water ballon. If you do nothing to it (isotonic solution) the ballon will not change (look the same). If you add water (hypotonic) it will get bigger in volume. If you subtract water (hypertonic) it will shrink in volume.

Finally, you just have to think about what shrinking or expanding a cells volume will do to it. Will it disrupt homeostasis?