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Fundamental Of Biology (BIOL 112) Osmosis Lab Report

Sandra Watson
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Lab Report, Osmosis and Diffusion

University of Louisiana at Lafayette

Fund Of Biology I Lab (BIOL 112)

Solutions, Diffusion, and Osmosis
Because all organisms are composed of one or more cells, the study of cellular interactions is
truly the primary focus of biology. Each cell possesses a semipermeable membrane, which allows certain
particles to flow in and out. Cells placed in solution, such as the blood cells found in the human body, or the
“pseudo-cells” used here in this lab, are directly affected by the concentrations of solutes and solvents in
those solutions.
In general, a solution is a mixture of solute dissolved in a solvent (BBC).Various concentrations of
solute would affect cells in various ways. For example, a cell placed in a solution of high concentration of
solute would experience a natural tendency to make this gradient more equal (particles more evenly
distributed) by diffusing the molecules from a higher concentration to a less concentrated area. Diffusion, by
definition, is “the result of the random movement of individual molecules (or ions) from a more
concentrated to a less concentrated region” (Patton 49). This occurs randomly and without the use of energy.
Also, the more concentrated a specific area is, the more rapidly the particles will diffuse to other areas, so
this rate of diffusion can be calculated (Patton 49).
Conversely, osmosis is “the net diffusion of water across a semi-permeable membrane” (Patton 50).
Water will diffuse from a region of low concentration of solutes to high concentration of solutes in order to
obtain a more equal ratio of solute to solvent. This process requires no energy, as diffusion, but it must be
noted that the solutes do not move, only water. Three types of general solutions can be observed: isotonic,
hypertonic, and hypotonic. When two solutions are isotonic to each other, the concentrations of solutes are
relatively equal. So, when a cell is placed into an isotonic solution, the flow of water into the cell balances
the movement of water out from the cell. Therefore, there is no net movement of water molecules across the
membrane. A hypertonic solution would have more solute than solvent, so water would flow from the cell
out to the solution, aiming to lower the relative concentration of solutes. Lastly, a hypotonic solution would
have a higher amount of water and less amount of solute, allowing water to flow into a cell to aim to balance
out the levels of solute inside the cell.
The experiment conducted in laboratory included observing “cells” placed in various solutions in
order to measure the movement of either solute or solvent. As solute in the cell, three concentrations of
starch (2.5x, 5x, and 10x) were used. Also, iodine was diffused in distilled water to track charged particle
movement into the cell. Each cell was made out of dialysis tubing, which served as a semipermeable
membrane. The lab groups were able to identify and track which molecules were crossing this membrane



Fundamental Of Biology (BIOL 112) Osmosis Lab Report

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