Elodea Lab Report

: A total of two different exercises were performed in the present experiment. A simulation of cells, using dialysis tubing, exposed to hypertonic, hypotonic, and isotonic environments, were setup in exercise one; and then observing the actual internal structure of wet mounts of plant cells, from Elodea, in isotonic, hypertonic, and hypotonic environments under microscopes in exercise two. The “cells” in the first experiment where tied ends of dialysis tubing, each containing 90% H2O / 10% NaCl solution. Their weight was measured. They were then exposed to three beakers of hypertonic, isotonic, and hypotonic solutions for one hour. Their weight was measured again, noting amount gained or lost. In the latter experiment, three Elodea leaves where

When a cell is immersed into a hypertonic solution, the tendency is for water to flow out of the cell in order to balance the concentration of the solutes. Likewise, a hypotonic solution has a lower concentration of solutes outside the cell than inside the cell. In an attempt to balance the concentrations of solutes inside and outside the cell, water will rush into the cell, and can cause it to burst (as explained above). A solute is the substance to be dissolved. The solvent is the one doing the dissolving. When plant cells are in a hypotonic solution, the central vacuole takes on extra water and pushes the cell membrane against the cell wall. Due the rigidity of the cell wall, it pushes back preventing the cell from bursting. This is called turgor pressure. An isotonic solution is one in which its effective osmole concentration is the same as the solute concentration of a cell. In this case the cell neither swells nor shrinks because there is no concentration gradient for water across the cell membrane (Colby,