isotooni

Isotooni refers to a state of balance in the concentration of solutes and water across a cell membrane, specifically when the internal and external environments of a cell have equal osmotic pressure. This condition ensures that there is no net movement of water into or out of the cell, maintaining cellular stability. The term derives from "isos" (meaning equal) and "tonic" (relating to tension or pressure), highlighting the equilibrium in osmotic tension.

In biological systems, isotoonic solutions are crucial for maintaining cell function. For example, in human physiology, red blood cells suspended in an isotoonic solution (such as 0.9% saline) retain their shape and integrity because the solute concentration matches that inside the cells. If a cell is placed in a hypertonic solution (higher solute concentration outside), water exits the cell, causing it to shrink—a process called crenation. Conversely, in a hypotonic solution (lower solute concentration outside), water enters the cell, leading to swelling or lysis if the cell cannot withstand the pressure.

Isotoonic conditions are commonly used in medical and laboratory settings to preserve cell viability. Intravenous fluids, such as normal saline, are formulated to be isotoonic to avoid disrupting cellular function during administration. This principle is also applied in agriculture, where isotoonic solutions may be used to study plant cell responses to osmotic stress. Understanding isotoonic balance is essential in fields like physiology, pharmacology, and biochemistry, where maintaining cellular homeostasis is critical for experiments and treatments.