Every cell is selectively permeable to different molecules. This type of selectively is caused by a semi-permeable membrane, which allows the movement of certain molecules across it. Water exchange can be measured in two ways: RBC osmotic permeability is measured, and diffusional water permeability is measured (Benga and Borza 1995). Diffusion is the movement of high concentration to low concentration. The diffusion of water across a permeable membrane is called osmosis. Water concentration in red blood cells can cause three different situations: hypertonic solution, isotonic solution, and a hypotonic solution. A hypertonic solution is when there is a higher concentration of salts dissolved outside the cell and pure water inside the cell, the water rushes out of the cell to try to dilute the salt solution causing the cell to shrivel up. An isotonic solution is where the water has achieved equilibrium with concentrations inside and outside of the cell, so there is no alteration of the cell. A hypotonic solution is where there is a higher concentration of salt dissolved inside the cell and a higher concentration of water outside the cell, so the water rushes into the cell trying to dilute it causing swelling of the cell. If this takes place too rapidly, it will lead to the cell bursting. Knowing the isotonic solution of red blood cells is important in many ways such as filtration because the membranes flux causes the cell to become larger or smaller so if it is too large it can not be filtered through certain size capillaries (Tuvia 1992). Also, red blood cells can only operate in an isotonic state, in a hypotonic solution the cell bursts leaving no cell at all, but in a hypertonic solution the cell shrinks, which decreases the surface area and its viability to uptake oxygen leaving it ineffective for its purpose. To measure the size and amount of red blood cells in each concentration of solutions, a hemocytometer was used.
Materials and Methods
Red
References: Benga G, Borza T. 1995. Diffusional water permeability of mammalian red blood cells. Comp. Biochem. Physiol. 112B(4):653-59. Tuvia S, Levin S, Korenstein R. 1992. Correlation between local cell membrane displacements and filterability of human red blood cells. Eur. Biophys. 304(1):32-6.