Lab Report Tonicity Osmosis in Red Blood Cells

Tonicity Osmosis in Red Blood Cells

Introduction

Gorter and Grendel (1925) had been the first to discover that the cell membrane is bilayer. Singer and Nicolson (1977) advanced the cell membrane structure by describing the existence and placement of proteins in the bilayer and developing the fluid mosaic model. The phospholipid bilayer is permeable to some substances in the mammalian cell membrane, such as oxygen and a small nonpolar molecule, and partially permeable to water. Still, some substances, such as charged ions and glucose, are impermeable without protein channels and transporters.

The phrase “selectively permeable” membrane was coined to describe the combination of phospholipid and protein characteristics (Goodhead & MacMillan, 2017; Gorter & Grendel, 1925). The tonicity of extracellular fluids, and thus the size and shape of cells resulting from osmotic water flow, is determined by the extent to which solutes may pass the cell membrane. The function and structure of cell membranes and the flow of substances over them are crucial to all biomedical science fields.

Diffusion is the molecules’ movement from a location where their concentration is higher to a region where their concentration is lower, according to the Human anatomy and physiology lab handbook (Marieb, 2012). Simple diffusion, enhanced diffusion, and osmosis occur in the cell membrane. The transport of molecules through the lipid bilayer is known as simple diffusion. The transport of substances through the plasma membrane with the help of a protein carrier is known as facilitated diffusion. However, this is still passive transport, meaning that no energy, such as ATP, is required.

In osmosis, the water molecules move from a higher concentration to a lower water concentration over a semipermeable membrane. The concentration of water is inversely proportional to that of the solute. As a result, we can define osmosis as water flowing from a lower to a higher concentration of solutes.

Living cells’ plasma membranes have the potential to receive or lose water from the extracellular fluid. Tonicity refers to a solution’s relative solute concentration compared to another solution. In terms of tonicity, there are three states. In a hypertonic solution, the concentration is higher than the concentration of intercellular fluid. A hypotonic solution is a concentration lower than that found inside cells. When compared to the inside of cells, an isotonic fluid has the same concentration. Water always passes through a semipermeable membrane from a hypotonic to a hypertonic solution.

The influence of a solution on cell volume due to the membrane’s permeability to that solute is referred to as tonicity. The osmolarity of the solute thus determines tonicity and whether it can pass the cell membrane; tonicity is determined only by the concentration of impermeant solutes. When comparing fluid concentrations to extracellular body fluid, the terms isotonic, hypertonic, and hypotonic are used instead of osmolarity since they represent the solution’s influence on cell volume, which is physiologically important (Goodhead & MacMillan, 2017). The tonicity will cause: no net water movement (isotonic), net water flow out of a cell (hypertonic), or net water flow into a cell (hypotonic).

In this laboratory experiment, therefore, the objective was to determine the tonicity of blood cells in three different types of extracellular fluids (hypertonic, hypotonic, and isotonic). The goal was to determine the change in the size of blood cells after being placed in each respective fluid for a certain period. The hypothesis in this experiment is that the change in the size of blood cells will be inversely related to the extracellular fluid concentration.

Materials and methods

Solutions and equipment required for the experiment were; 10% NaCl Solution, 0.9% NaCl solution, distilled water, at least three sterilized vials/test tubes, microscope and at least four sterile slides, pipettes, mammalian blood, marker pen, stopwatch, and writing materials (pen and a sheet of paper).

Procedure

Each of the three vials was marked, i.e., 10% NaCl, 0.9% NaCl, and Distilled water. A fraction of each solution was transferred to the respective vial using different pipettes. Next, the same amount of mammalian blood was introduced to each vial. The mixture was shaken to ensure thorough mixing of the solution then left undisturbed for thirty minutes.

After the wait time, the appearance of the mixture in each of the three vials was observed, and the observations were noted down on a sheet of paper. Next, a drop of the solution from each of the three vials was placed on a slide and observed under a microscope, and an image of each sample was produced as experimental data. (Specific details of the methodology are outlined in the lab manual).

Results

Table 1: Observations made for the blood cells after being placed in varying NaCl and Distilled water concentrations.

10% NaCl

0.9% NaCl

Distilled water

Vial Transparency

Cloudy

Cloudy

Clear

Microscope Cell appearance

Crenate

Normal

Burst

Tonicity

Flypertonic

Isotonic

Flypotonic

Image

Discussion

Blood cells in a 10% NaCl solution were exposed to a hypertonic solution compared to plasma. When the red blood cells are positioned in a hypertonic solution, the bathing solution’s higher effective osmotic pressure than the internal fluid causes water to migrate down its osmotic gradient and out of the cell via osmosis (Lindinger, 2022). Consequently, red blood cells lose their biconcave structure and shrink or crenate. Because the cells take up less space due to the quick loss of water, the solution’s packed cell volume, or hematocrit, decreases.

In the 0.9% NaCl solution, blood cells were exposed to an isotonic solution (osmolarity 286 mosM). Because the intracellular fluid has an osmolarity of roughly 286 mosM, osmolyte particles are evenly distributed across both sides of the cell membrane in this environment. As a result, there is no net water flow between the soaked red blood cells and the NaCl solution. The solution’s hematocrit should be unchanged, and the value should be comparable to that of nonhemolyzed blood. Similarly, there should have been very little, if any, hemolysis of the red blood cells.

Complete hemolysis occurred in blood cells washed in distilled water, and the projected percent hemolysis should have been 100%. Because there were no ions in the bathing solution, it was exceedingly hypotonic, allowing water to flow into the red blood cells via osmosis, causing all of the cells to lose their membrane integrity and hemolyze, releasing hemoglobin into the supernatant (Goodhead & MacMillan, 2017; Ibarra & Foresto, 2021). Because there were no leftover complete red blood cells to contribute to packing cell volume, the adjusted hematocrit was 0%. The cells burst and no longer impede light flowing through the fluid since distilled water is hypotonic; therefore, the observation is ‘clear.’

These results are relevant, especially in patient care, as the tonicity of drugs is an important aspect of administering drugs. Hypertonicity causes fluid to be transferred from inside body cells to the surrounding fluid compartment. Hypertonicity has serious clinical consequences linked to death and significant short- and long-term neurological consequences (Rondon-Berrios et al., 2017). Hypernatremia and hyperglycemia are the two most common hypertonic clinical disorders. A relative excess of sodium causes hypernatremia compared to the amount of water in the body. Hypernatremia is caused by a loss of water over intake, a gain of sodium salts over losses, or a combination of the two.

Maintaining a consistent volume is critical in clinical settings to ensure effective function and survival of bodily cells. The ability of cells to extrude solute into the extracellular compartment and the high permeability of cellular membranes to water results in the regulation of cell volume under normal conditions (Argyropoulos et al., 2016). Tonicity (effective osmolarity) disturbances are the most common clinical diseases that influence cell volume. Hypertonicity induces cell shrinkage, which results in severe clinical symptoms and even death. The volume of hypotonic fluids required to rectify a particular level of hypertonicity is calculated using formulas in quantitative hypertonic disorder management.

One of the elements that impact medication absorption is tonicity. In the presence of hypertonic fluids, epithelial cell shrinkage is a regular occurrence. On the other hand, hypertonic saline solutions limit ciliary function as well. Because the tonicity of the drug’s delivered form has a major impact on the nasal mucosa, isotonic preparations should be used for the best results.

A healthcare practitioner who understands the tonicity and pH of a drug should be able to modify the tonicity appropriately to avoid any unwanted effects on the patient when the drug is administered. There are various methods available to a healthcare practitioner to adjust the tonicity and pH of a drug to make it safe for a patient while at the same time allowing for maximum absorption of the drug into the cells for maximized effect in bringing about the desired health effect.

In this experiment, the primary variables were Blood Cell Size and NaCl concentration. The experiment’s working hypothesis was that the change in the size of blood cells would be inversely related to the extracellular fluid concentration. This means that an increase in the size of blood cells will be witnessed in the distilled water, while a decrease in the size of blood cells will be witnessed in the high concentrated NaCl.