14. Paramecium cells are protists with no cell walls. Paramecium\'s internal osm

Question

14. Paramecium cells are protists with no cell walls. Paramecium's internal osmolarity (solute concentration) of the cell is about 300 mosM/L. The osmolarity of freshwater is about 30-40 mosM/L. For this reason, Paramecium possess contractile vacuoles, organelles that constantly collect and eject water from the cell. What would happen to the Paramecium if it did not have contractile vacuoles? And why? Practice using the terms hypertonic, ete. in your explanation 15. You are stranded on a lifeboat in the middle of the Pacific Ocean. You are extremely thirsty because your water supply has run out. Explain (in terms of osmosis) why you should absolutely NOT drink the salty sea water (1200 mosM/L), no matter how thirsty you are. (Hint: Think about all that salt absorbed into your blood stream. How would the red blood cells (300 mosM/L) be affected?

Explanation / Answer

Water potential of pure water is the highest which is set at zero.

Water potential of any solution is negative. Greater the solute concentration more negative is the water potential.

Water moves from high water potential to low water potential.

Water moves from hypotonic to the hypertonic solution.

14.

Osmolarity of Paramecium = 300 mosM/L

Osmolarity of fresh water = 30 mosM/L

So, if we place a Paramecium in freshwater, the cell will bulge and rupture due to endosmosis of water. To prevent this, Paramecium contains contractile vacuoles which maintain optimum osmotic potential.

15.

Osmolarity of RBC = 300 mosM/L

Osmolarity of Pacific Ocean water = 1200 mosM/L

So, if we drink ocean water, our RBC will be subjected to the hypertonic condition which eventually leads to the shrinkage of cells due to exosmosis of water.

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