Experimental Procedure:
Refer to lab manual (page 54-55) in Nelson Biology 11.
Results/Observations:
Table 1: Color of the solution or Suspension
Table 2: Test for glucose.
Conclusion:
As a result of the glucose test we are able to see that the glucose of dialysis tube is now presented in dilute Lugol’s solution in beaker. We also notice that the iodine of beaker’s solution is entered in dialysis tube’s starch. So overall, its proved that there’s been reaction occurred in both solutions of dialysis tube, but there is no change or reaction in the test tubes’ solutions. This all concludes that glucose and iodine were small particles and starch was the largest particle of this lab. The dialysis tubing acted as a semi permeable membrane by allowing small particles to diffuse.
Discussion:
The use of dialysis can make it very easy for use to understand diffusion and osmosis in cell membrane. In this lab we discovered the particle that can or can’t pass through the cell membrane. In our lab we had dilute Lugol’s solution in beaker and in two dialysis tubes we had glucose solution and starch suspension.
While we were doing the lab we found out that iodine has moved from dilute Lugol’s solution in the beaker into the dialysis tube. We know that dilute Lugol’s solution is made up of iodine and water. Scientifically when starch reacts with iodine the solution turns little black. So this statement is enough to prove that iodine has diffused into dialysis tube from the beaker. But we also had starch in test tube, then why didn’t that change its color? Now we come across to the prediction that small particles can pass through dialysis tube and not the test tube.
At the end of the lab when we did glucose test using Fehling’s solution, and we see that dilute Lugol’s solution has changed into orange color, which proves that there is glucose presented in solution. But dilute Lugol’s solution is made up of water and iodine, and we can say that the glucose in dialysis tube must have been diffused into beaker, because only solution in dialysis tube contains glucose.
During our lab we figured out that glucose diffused in dialysis tube and didn’t in test tube, because when we did glucose test the color of solution in beaker changed to orange, but solution in test tube stayed blue. This shows that even small particles can’t pass through strong or thick surface. Overall, the function of having test tube with Lugol’s solution was to show that some surface’s allows things to diffuse through it, where some surfaces don’t.
The function of putting test tube with the starch suspension was as same as function of putting test tube with dilute Lugol’s solution. Also in this part we see that iodine was presented in dialysis tube’s starch suspension but wasn’t in test tube’s starch. This also proves that molecules like glucose and iodine can pass through cell membrane, but can’t pass through cell wall.
In this lab dialysis tube is shown as cell membrane of our body. In our body small particles like water, glucose and iodine can pass through surface of cell membrane. In this experiment the dialysis tube works as same way as cell membrane because small particles also passed through it.
Throughout this whole experiment we came to find out the small particles and large particles. The largest particle of this experiment is starch. We know that starch turned black when it was placed in dilute Lugol’s solution. We also know that glucose left dialysis tube and mixed with beaker’s solution. That’s why it shows that neither glucose nor iodine is largest. So the presence of starch in dialysis tube proves that starch is the largest particle here.
Sources of Experimental Error.
Since this experiment was done by a human and not by a robot it was usual that there should be a source of error. While we were doing this lab we faced some problems that affected our experiment. We had some minor problems that didn’t do much bad, but our major problem wasted our time, which we lacked. In this lab we had to tie two ends of dialysis tube tightly, but by mistake there was a lose point in our dialysis tube of starch. This leaking of starch was ruining beaker’s solution and as well as our solution, which made lab worth no use. So to have a good lab we had to everything again which wasted a lot of time, but still we covered it all and got it all right. The other problems like usage of contaminated solution and amount didn’t matter a lot, so it was fine. But, as a result our lab was a great success.
