A solution with a higher solute concentration than a cell is known as hypertonic solution. A solution of lower solute solution than the cell is known as hypotonic solution and of similar concentration isotonic solution. Osmosis refers to the phenomenon whereby solution moves from a hypotonic area, across a membrane with selective permeability, to a hypertonic area. The selective membrane refers to membranes that prevents one substance from passing through but allows another. In most cases, the biological membranes are permeable to water and impermeable to solutes such as sugars and ions. The cells have an ability of regulating their internal water and salt concentration in order to their ideal environment. This is called osmoregulation (Bowen).
When a cell is put in a solution that is hypertonic, the solvent in the cell is forced out from the cell into the surrounding environment. This osmotic effect causes the cell to undergo shrinking. If the surrounding area has less solute concentration than the cell, the osmosis will take place resulting in the cell acquiring more solvent. In the isotonic solution, there is no net solvent movement. The cells in such a solution do not shrink or swell. Red blood cells are surrounded a cell membrane that is semi-permeable and allows water to pass through while restricting passage of many of the hydrophilic solutes. The movement of water in or out of these cells is usually enhanced by in the total concentration differences between the solutes on both sides (Bowen).
This experiment was done with an aim of demonstrating the influence isotonic, hypertonic, and hypotonic solutions in the red blood cells. This was done using red blood cells from an animal. The study hypothesized that different solution concentrations affect the size and shape of red blood cells.
Materials and Methods
In the study animal, red blood cells were used as the experimental cells. Clean slides and covers were used to hold the cells and while 10% sodium chloride solution was used to make up the hypertonic solution. Distilled water was used to make up the hypotonic solution while a microscope was used to monitor the cells during the experiment.
In the first method, a slide was placed on the bench and a small drop of red blood cell carefully placed on the slide’s center. The slide was covered with a cover slip and immediately placed under the microscope (high-power lens). The cells were viewed, and the data observations noted.
In the second method, a 10 % sodium chloride solution was placed at the slide’s edge and the red blood cell added carefully. The slide was covered with a cover slip and placed under the microscope. The cells were viewed, and the data observations noted.
In the third method, a new slide was taken and a small drop of red blood cell placed on it. A drop of distilled water was carefully added at the edge cover slip and under the microscope. The cells were viewed, and the data observations noted.
The sizes and the shape of the red blood cells in the three different methods are as below (Table 1). In the first method, the cells did not change either in shape or in size. In the second method, the cells became smaller in size while their shape was crenated. In the third method, the cells were bigger in size and after sometime, they erupted.
Animal red blood cells are biconcave in shape. The three different methods offered the cells three different environments. In the first method, the cells were in an environment that has the same solute concentration as the cells. This solution may thus be referred to as an isotonic solution. When the cells are in such environment, there is little net movement of water and hence no change in size or shape of the cells. In the second method, 10 % solution of sodium chloride increased the solute concentration in the surround making it higher than that of the cells. As a hypertonic solution, this environment causes water to move out of the cell through osmosis. Consequently, the cell is reduced in size and its shape is crenated.
In the third method, distilled water turned the environment surrounding the cells into a hypotonic environment. In such an environment, the cells gained water through the process of osmosis. Water entered rapidly causing the cells to in swell and finally bursting. The phenomenon where a cell bursts after gaining water through osmosis is known as haemolysis (Bowen).
The results supported the hypothesis that different solution concentrations affect the red blood cell’s size as well as shape. An experiment where the weight of the cells before and after the experiment is measured might be useful in giving more support to the hypothesis.
These observations offer a number of significant practical implications especially in hospitals. When storing the red blood cells or other cells, it is important to store them in a plasma solution with the right proportions of proteins as well as salts. The plasma solution required to be of a slightly higher concentration than what is in the cells in order to maintain the integrity of the cell while preventing haemolysis. In addition, when administering dug intravenously, it is important to suspend in a solution that is hypertonic to red blood cells. If the drug is injected using a solution that is hypotonic to red blood cells hypotonic, the red blood cells of the patient may undergo haemolysis (Bowen). The stage of haemolysis occurs in stages. The cell starts by swelling followed by popping. The cells then reduce in volume due to ion leakage and lastly hemoglobin leakage takes place (Jay and Rowlands).
Bowen, Richard. Osmosis. 2000. 31 January 2013
Jay, A. W. and S. Rowlands. “The stages of osmotic haemolysis.” J Physiol. 252.3 (1975): 817-32.