What should the initial number of dextrose and water molecules in your IV Fluid be for the extracellular fluid to be isotonic to the cell?

Answer 1

Answer: The extracellular fluid (ECF) is always isotonic to the cell (in in vivo systems), but, in in vitro conditions the ECF is diluted in the buffer solution used to maintain the cells, generally this solution has a low quantity of ions (just enough concentration so it isn’t toxic for cells cultured) and therefore has a low osmotic potential (?s), that’s the reason to add dextrose (also called glucose, a monosaccharide) or sucrose (a disaccharide), which are solutes that don’t increase the ionic force of the solution but do increase the osmotic potential.

Since you’re not providing the value of the osmotic potential of the ECF or the cells (which is something common) the lab procedure you should use is the following:

1) Measure the dimensions of the cells you’ll work in in vivo conditions with an optic microscope (height and width).
2) Prepare a lot of solutions (ranging from 0,01 M to 3 M) with dextrose and water.
3) Place some cells in each solution and then check on the microscope their dimensions (if you can measure them would be ideal, if not, then it should be enough the classes “smaller, no change, bigger” according to their volume).
4) The concentration of solutions (or the interval of solutions) where you aren’t able to see changes in cell’s size is the one that has the same osmotic potential as the ECF.