Osmosis Lab

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Background:
In order to maintain homeostasis a cell must be able to transport materials back and forth across its membrane. This movement is regulated because a cells membrane is selectively permeable, which means that some substances can pass through the membrane while others cannot. Both solutes and solvents can move across the cell membrane.
Diffusion is known as the movement of a solute from areas of high concentration to an area of lower concentration. Diffusion is quite simple since molecules and ions are constantly moving, and will eventually collide with one another. The higher the concentration of a molecule the greater the number of collisions will be. Collisions cause the molecules to change direction and to spread out until they …show more content…

To describe the relative concentrations of different solutions the terms hypotonic, hypertonic and isotonic are used. A hypotonic solution is one that has a higher concentration of water and a lower solute concentration, while a hypertonic solution has a lower concentration of water and a higher concentration of solute. Both these solution represent unequal concentration of molecules on either side of the membrane and will result in a net flow of water by osmosis to equalize the side’s concentrations. Correspondingly, two solutions are considered to be isotonic when equal concentrations of solute and water exist on both sides of the …show more content…

Get five plastic cups and label them with the solution they are holding using a permanent marker.
2. Obtain five 18-cm pieces of pre soaked dialysis tubing.
3. Twist and tie one end of the tubing into a knot.
4. Using a graduated cylinder and pipette measure 15 mL of the specific solution listed for the Model Cell in listed in the table below.
5. Open up the opposite end of the dialysis tubing by rubbing it together between your finger tips (this works best if the tubing is still wet)
6. Use a pipette to pick up the solution form the graduated cylinder and transfer the solution into the dialysis tubing.
7. Twist and knot the open end of the dialysis tubing to complete the model cell
8. Place the dialysis tube bag on a paper towel and gently roll it back and forth to remove any excess liquid from outside of the bag.
9. Measure and record the mass of the dialysis tube
10. Place the dialysis tubing into the cup it corresponds with
11. Fill the first cup with the solution indicated on the outside of it until the solution completely covers the model cell placed inside.
12. After 24 hours remove the dialysis tubing bag from the cup. Once again gently roll it back and forth on a paper towel to remove excess liquid. Measure and record the final mass of the dialysis

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