The purpose of this experiment was to observe the process of diffusion of substances across a semipermeable membrane to gain a better understanding of how cells move materials across cell membranes. The experiment was designed to exhibit Brownian Motion; the random movement and tendency of particles of a substance to move from an area of greater concentration to lower concentration via diffusion until equilibrium has been attained. In addition to observing the passive process of diffusion, the experiment demonstrated how a semipermeable membrane will only allow certain substances to diffuse across a membrane. Materials Needed
2 pieces of thread
8 test tubes
2 disposable pipets
IKI dropper bottle
Silver nitrate dropper bottle
Barium chloride dropper bottle
A piece of dialysis tubing was procured and a knot was tied at one end. 2.
A funnel was inserted into the open end of the dialysis tube and it was filled with a solution consisting of 1% starch, 1% albumin, The air was then eliminated and the open end was tied with another piece of string. 3.
The dialysis tube was rinsed with tap water and placed in a culture dish, the tautness of the tube was documented, and the initial solutions inside the bag were recorded. 4.
A sodium sulfate solution was poured into the culture dish until the dialysis bag was fully submerged. 5.
The dialysis tube remained in the culture dish immersed in solution for approximately 40 minutes at which time it was removed from the culture dish and tautness was again observed and recorded. 6.
The dialysis tube was rinsed with tap water and the contents were emptied into a 100mL beaker. 7.
Eight test tubes were cleaned and labeled.
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