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 solutions 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 membranes 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 solutions 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...

As witnessed and recorded in table 1 above, blood cells placed in high concentration (10%) NaCl underwent crenation while blood cells placed in distilled water expanded to a level of compromising the integrity of the cell membrane; thus, cells burst. This observation is in li9ne with the hypothesis; thus, it has been held as correct that the change of the size of blood cells is inversely related to the concentration of the extracellular fluid they are bathed.

Conclusion

When red blood cells are exposed to a hypertonic solution, the osmotic pressure outside the cell is higher than inside the cell. As a result, a process known as osmosis causes water to migrate out of the cell. The cells will lose their original form and may contract. When cells are exposed to an isotonic environment, the inner and outside pressures are equal. As a result, there is no water movement out of or into the cell, and it maintains its shape.

Water travels from outside the cells into the cells via osmosis in hypotonic conditions, causing the cells to expand and burst (hemolysis). As a result, the cells will be harmed, and their function, such as oxygen-carrying capacity, may be reduced. A good grasp of tonicity offers a healthcare practitioner a better understanding of how dehydration affects the bodys cells. In an isotonic solution, because the osmotic pressure inside and outside the cell is equal, there is no net water movement, and the cells keep their structure and function.

The findings and conclusions that are a part of this experiment are crucial for understanding basic cell physiology. Students will appreciate the notion that cell membranes are selectively permeable and that fluid tonicity and osmolarity affect cell size and structure if they understand the ideas presented in this practice. This is critical to gasp the notion of homeostasis, such as when studying the gastrointestinal tract, the management of NaCl by the nephron in the renal system, and, in…