Diffusion and Osmosis Lab

1A - Diffusion

Purpose

The purpose of the lab was to evaluate the diffusion of both large and small molecules through a semipermiable membrane.  We were testing to see if glucose would diffuse through the dialysis tubing.  The independent variable was 

Introduction

Diffusion is the random movement of molecules from a higher concentration to a lower one.  Osmosis is a specific type of diffusion, which involves water.  The movement of ions and molecules is not completely due to diffusion and osmosis, but also because of active transport.  Active transport moves a substance from a lower concentration to a higher one.

Methods

By taking dialysis tubing, which is semipermeable, filled with a glucose and starch mixture, we looked to see which substances would pass through the tubing from the water and iodine mixture it was submerged in.

Dark purple liquid within dialysis tubing, sitting in iodine solution. (After reaction)

Indicators for the presence of glucose throughout experiment.

Data

Discussion

Our results from this lab helped to further prove the laws of diffusion, osmosis, and the ability of membrane pore sizes to allow molecules to either pass or not pass through. From our data we can conclude that molecules in areas of high concentration will always move (diffuse) to areas of low concentration unless the molecules are too large to pass through the membrane or the membrane pores are too small. We know this to be true due to the fact that the contents inside the dialysis tubing and in the beaker had changed color by the end of the lab. Before the lab had begun, the beaker solution was a red/orange color and the dialysis tubing solution was clear. At the end of the experiment, the beaker was still a red/orange color but thr dialysis tubing solution had turned a purple color. This change in color was a result of the diffusion of iodine into the tubing. Iodine entered the tubing and glucose left the tubing. If we were to change or improve anything about this lab we would want specific amounts of solution (water, glucose, starch, etc.) so we could know how much to add to get even more accurate results. To conclude, our results were seemingly accurate and met the criteria of the laws of diffusion.

Conclusion

We found that glucose travelled from inside the cell to the solution. This means, in respect to the glucose, this was a hypertonic solution. Overall, this indicates iodine and starch cannot pass through the membrane as easily as glucose can.  The dark purple a appearance of the bag's contents indicates a change in the solution and solute. 

References

http://www.uic.edu/classes/bios/bios100/lecturesf04am/lect09.htm

1B - Osmosis

Purpose

Determine the water potential within a potato cell (plant cell), the different molar concentrations of sucrose that the potato cores are placed into determine this.  The independent variable is the molar concentrations of sucrose and the dependent variable are the potato cores. The change in sucrose helps to see the change in water potential. 

Introduction

Water always moves from area of high water potential to an area of low water potiential, meaning that water moves from an area with a lot of water to an area with little to no water. the water potential itself is affected by solute and pressure being added to or taken away from an area.  

Methods

Data

Discussion 

Our results from this lab helped to prove the laws of osmosis, the diffusion of water. Just like diffusion, osmosis strives for equilibrium. When a solution is hypotonic this means that it has a low level solution and a high level of water. When a solution is hypertonic this means that is has a high level of solution and a low level water. In order to reach equilibrium, more water is required in hypertonic solutions and less water is needed in hypotonic solutions. Water always diffuses from an area of high concentration to an area of low concentration. This is proved in our lab because after soaking different solutions of sucrose in dialysis tubing that was submerged in water, the masses of the tubing changed. Osmosis had occurred. If we were to repeat this lab and improve it, we would have measured the solutions more precisely in order to get more uniform answers and would have also been more careful when drying and weighing the solutions in the dialysis tubing. The results of our lab further prove the laws of osmosis. 

Conclusion

References

1C - Water Potential 

Purpose

Introduction

Methods

Coring the potatoes.

Data

Discussion

Our results from this lab helped us determine the water potential of each potato cell and what water potential really is. Our data proves that areas of high water potential will always move to areas of low water potential. Water potential is affected by two things; pressure potential and solute potential. Our data also proved that water potential and solute potential are inversely related. If solute potential is high then water potential will be low and vice versa. Our data is seemingly accurate due to the fact the fact that these points were proven. If we were to improve any aspects of this lab we would Improve the measurements. Not all potato cells/solutions/etc. we're exactly the same. This means that not all data corresponded to each other. This means that the results were a bit more difficult to compare and contrast. Overall, this experiment went well and got accurate and favorable results. 

1E

Disscusion

Plasmolysis is movement of water out of the plant cell and shrinking of the of the plant cell due to the loss. The water that is diffused out of the cell goes into a hypertonic solutionthat is surrounding the cell.  The space between the cytoplasm and the cell wall is filled with the exertonic solution. Because an oninon cell is a plant cell and the area around the onion has a lower water potential so the  water would move out of the cell. If plant cells are exposed to a hypertonic solution such as salt water, the water in the plant cell is drained  from the cell and into the hypertonic salt water around it.

Refrence

http://biologymadesimple.com/topics/absorption-by-roots/absorption-by-roots-page-4/