The Effect of Different Percentages of Saline on the Largest Diameter of Human Erythrocytes

By Alykhan Rajan
Intermediate Category (Grades 9-10)
Experiment | Biology, Chemistry

BCVSF Note: The required ethics forms have been submitted for this project.

This experiment was performed to investigate how adding isotonic, hypotonic, and hypertonic solutions affected the largest diameter of human erythrocytes. In this experiment, 0.9% saline was used as an isotonic solution, 0.45% saline was used as a hypotonic solution, and 3% saline was used as a hypertonic solution. All of these solutions are used in the hospital setting to treat various conditions. As these solutions often enter the body through an IV and therefore go directly into the bloodstream it is important to understand how these solutions can affect the blood cells.

In this experiment, blood was taken under medical supervision and the solutions mentioned above were added to the blood. The average largest diameter remained relatively consistent when an isotonic solution was added to the erythrocytes. However, when a hypotonic solution was added the erythrocytes increased in size. This was due to osmosis. Osmosis is the movement of water from a higher concentration to a lower concentration of solute through a semipermeable membrane. In this experiment, the solute was the saline and the semipermeable membrane was the cell membrane to achieve equilibrium. Equilibrium is when the concentration of solute is the same on both sides of the semipermeable membrane The water moved from the extracellular space with a lower concentration of solute to the intracellular space with a higher concentration of solute through the semipermeable membrane the cell membrane. This increase in water in intracellular space caused the erythrocyte largest diameter to increase. When the hypertonic solution was added the largest diameter of the erythrocytes decrease as water moved from the intracellular space with a lower concentration of saline to the extracellular space with a higher concentration of saline causing the largest diameter of the erythrocytes to decrease.

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