Osmosis:Choose the right solution for an intravenous drip

Choosing an IV fluid

You will meet Frank in the hospital. He is dehydrated because of sunstroke and needs extra fluids. There are three solutions available, but which one is the correct one to avoid damaging Frank’s blood cells?

Finding the isotonic point

Join Dr. One in the lab to understand exactly how water is transported across the cell membrane in osmosis. An animation will show you how the solute concentration of a solution can be equalized through diffusion and osmosis. You will see how solutes can move through the solution via diffusion and how water is transported across a semipermeable membrane in osmosis. You will then place potato cubes in a serial dilution of saline to see how water moves either into or out of the cells depending on the salt concentration.

Once you have plotted your results, you will be able to identify the isotonic point where the salt concentration of the solution is exactly the same as the salt concentration inside the cells. You will also see in which direction the water moves in both a hypotonic and a hypertonic solution. Finally, you can see the effect of hypotonic and hypertonic solutions on cells by adding these solutions to a blood sample and observing the red blood cells under the microscope.

Back to the hospital

After your experiments, you fully understand the three saline solutions that were available to Frank and the effect that the salt concentration will have on the cells in his blood. Review your hypothesis and advise Frank and his doctors on the correct IV solution.