Iodine And The Benedicts Test example essay topic

Salivary Amylase Lab In this laboratory, I observed the process by which salivary amylase, an enzyme secreted by the salivary glands in the mouth, breaks starch down into maltose. This requires a relatively straightforward experiment with only a couple of indicators, some test tubes, and a starch source. To understand the process, one has to understand chemical reactions with enzymes and the its major role in the digestive system of the human (Chapter 37). Just to refresh the reader, I will define a few words that will appear later on in the lab. Starch is complex compilation of simple sugars (or a polysaccharide) that when broken down into simpler substance, forms two-sugar maltose (a disaccharide).

The enzyme required to break down starch, only by simple mixing, is salivary amylase, as described above. The two indicators used in this experiment are chemicals that indicate the presence of the corresponding substances, starch and maltose. Iodine indicates starch with a color change from reddish-brown to black. Benedicts indicates maltose with a color change from translucent blue to orange-yellow (with the aid of heat). I will give my hypotheses and the predictions for the results of the experiments. The first experiment called for the mixture of saliva and oatmeal in two test tubes, one for testing starch and one for testing sugar.

I hypothesize that the iodine will indicate positive for starch and the Benedicts will indicate positive for maltose. The second experiment called for the testing of saliva for starch and sugar, in separate test tubes. I think the test of iodine and Benedicts will both be negative. The third and final experiment is a mixture of oatmeal and H 20 (water); I predict the Method In this lab, the following materials were used to understand better enzymatic / digestive activity with saliva: -Pinch of Oatmeal -Mortar and pestle -A volunteer to supply the needed saliva -Saliva (mL) -Six test tubes -Preferably Distilled Water (mL) -Five drops in each test tube of Benedicts Solution -Five drops in each test tube of Iodine -Tube rack -Hot plate -Beaker with boiling water put on hot plate Procedure & Results This section gives a systematic, detailed explanation on how the experiment was carried out and what happened afterwards. NEXT PAGE NOTE: I will sometimes refer to maltose as sugar (and visa versa) as according to the experiment. Procedure SET UP TEST TUBES LIKE SO: 1) Make sure the proper materials listed above are prepared (put tubes in tube rack and start setting up the boiling water beaker) 2) Place the required amount of oatmeal in the mortar and pestle and start grinding the oatmeal into a powder.

3) At the same time let the volunteer (s) rinse their mouth with water from the water fountain and then begin to drain saliva into the designated beaker. 4) When finished with the drainage, put the correct amount of saliva into the corresponding test tubes. 5) Take the powdered oatmeal and place it in the designated test tubes. 6) Take the predetermined amount of water and put it in the designated test tubes. 7) Place five drops of Benedicts in each of the designated containers and place the tubes in the heated beaker for a few minutes or until results. 8) Record results.

9) The next step is to place five drops of iodine in the designated test tubes and wait for results. 10) Record results. 11) Experiment procedures are complete. Results & Discussion By comparing all of the results, one can tell that most of my hypotheses were correct. I will start by listing the results explaining how I came across these amended hypotheses. (+) and (-) stand for positive and negative test results Iodine = test for starch, Benedicts = test for sugar Saliva & Oatmeal TT 1: Iodine (+) / Color - blue / black TT 2: Benedicts (+) / Color green / orange Saliva TT 3: Iodine (-) / Color Yellow TT 4: Benedicts (-) / Color Blue Oatmeal & H 20 TT 5: Iodine (+) / Color blue / black TT 6: Benedicts (-) / Color blue I predicted that the mixture of saliva and oatmeal would yield positive results for both the iodine and the Benedicts test. My hypothesis was correct.

My next prediction was that the iodine and Benedicts tests for saliva would both turn out negative; I postulated correctly again. The last pair of tubes containing a mixture of oatmeal and H 20 were also tested with iodine and Benedicts; I predicted that the iodine would be positive but the Benedicts would result negative; I was correct once again in my hypotheses. I will now discuss how I came to these predictions. The first test was with a mixture of saliva and oatmeal. I realized almost immediately that sugar, and also starch, would be present. I learned from Chapter 37 in the textbook the enzyme salivary amylase in saliva would react and break down most of the starch in the oatmeal into maltose.

The reason not all of the starch was broken down was because I also learned previously that an enzyme (salivary amylase) can only handle so much of the given substrate (oatmeal starch) before it is exhausted. So, I was right in thinking that there would be an indication of both maltose and starch. In the second test, I knew right away that there wasnt going to be any starch or sugar in the saliva because: 1) The volunteers rinsed their mouth out before the experiment. 2) The saliva contains only the enzyme and not the substrate or product. So, the saliva definitely did not have starch or sugar.

And finally there was the test with the oatmeal and water. I know that the oatmeal contains starch and not maltose and the water does not have any of these substances. This test was merely to show that oatmeal had starch, which the positive iodine test proves clearly. To conclude, I would like to say that I feel this was the most lucid and clear laboratory that we have done up to this point and there really shouldnt be any changes to it.