Starch and Saiva Starch and Salva Water and Saliva Starch staran Todine RIGURE 6

Question

Starch and Saiva Starch and Salva Water and Saliva Starch staran Todine RIGURE 6.2 Experimental setup. After at least 60 minutes add KD Benedict's Benedict's and Heat and Heat Part A: Materials and Experimental Method 1 Working with your lab group, obtain the following supplies 1 test tube rack - 1 grease pencil SAFETY NOTES 5 clean test tubes 1 Never pour any liquids down the drain Graduated cylinders Benedict's solution dispose of liquid waste in the labeled container in the fume hood. Starch solution a lodine solution 3 Return supplies to the side counter. Place empty, but dirty, test tubes in the labeled container on the side counter. Synthetic saliva or amylase solution Number the test tubes 1 through 5 with a grease pencil. Follow these instructions and refer to the diagram in Figure 6.2 to set up the experiment. a. Add 5 mL of dilute starch solution to test tubes #1 through #4. . Add 5 mL of water to test tube #5. b Add 1.5 mL of synthetic saliva to test tubes #3 through #5 and mix the contents. 2 3 stand in the rack for at least 60 minutes (the experiment can run for longer than 60 minutes). might take place in each Record your incubating, propose a hypothesis (in the "If...Then.." form) for the reaction that rubes re f the tubes and predict whether or not the lodine or Benedict's test should be tubes and ht take placeUse your knowledge of enzymes and their function as a basis for your hypotheses.) in the results table under the "Expected Results" column for each tube. iction

Explanation / Answer

1. Test tube 1 will show a blue-black colur as tube 1 contains starch which react with Iodine-potassium iodide solution and gives blue-black colour. The observation of blue-black colur indicates a positive test for presence of starch.

2. Test tube 2 will not show a change in colour because Benedict's solution does not react with starch. Benedicts solution only reacts with reducing sugars like glucose and fructose. Thus, the colour will remain aqua blue (colour of benedicts solution) which indicates negative test for presence of reducing sugars.

3. Test tube 3rd will show no colour change. Here, the enzyme amylase present in synthetic saliva will degrade the starch into simple sugars (monosaccharides). Monosaccharides and disaccharides do not react with iodine and thus a negative test for presence of monosaccharides or reducing sugars will be observed.

4. Fourth test tube will show a change in colour from aqua blue to yellow to orange. Here, monosaccharides produced by action of amylase on starch will react with Benedicts solution and a colour change will be observed.

5. No colour change will occur as there is no starch or any kind of sugars in the 5th test tube.

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