Exp+enzymes - lab report PDF

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EXPERIMENT

1) Amylase a) Collect about 5 drops of saliva (which contains amylase) into a small dixie cup. Then mix about two drop of the saliva from dixie cup with 2 mL of distilled water in another dixie cup. This is your saliva solution. b) Fill a 400 mL beaker 2/3 full of hot tap water. (Should be around 35º C). This temperature needs to fairly constant for optimal enzyme activity. c) In a test tube add the saliva solution (from a) to 4 mL of a 1% starch solution and stir. d) Take a few drop of the saliva-starch solution (from c) on a watch glass and add 1 drop of an iodine solution. Record the initial color. [Blue-black = starch, yellow = glucose or maltose] e) Place the test tube (from c) containing saliva-starch in the water bath (b) Make sure temperature of water bath is still around 35º C. Every 2 or 3 minutes remove a few drops of the solution and perform the starch-iodine test (step d) f) When the starch-iodine test is negative (record the times on the lab report) confirm the presence of reducing sugar using the Fehling’s test.

Fehling’s test. Making the Fehlings solution for 1 test: Using a 10 mL graduated cylinder, get 1 mL of part A and 1 mL of part B. Using the Fehlings solution: Take the 2 mL of the above Fehlings solution and add it to a medium sized test tube with remaining saliva-starch solution (from c) to be tested for a reducing sugar. Stir. Place the test tube in a boiling water bath for at LEAST 10 minutes. A brick red ppt is a positive test. (A trace of Cu2O is not a confirmation)

600 mL beaker with water on a hot plate.

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2) Catalase Use a prepared sweet potato extract (which was prepared by blending and filtering through a cheese cloth and then diluting with distilled water). Get 50 mL of extract in a 150 mL beaker to use for parts “a to f”.

You will make some quantitative observations on the rate of decomposition of hydrogen peroxide catalyzed by the enzyme catalase. Set up the apparatus as shown in figure 3 above. Fit a CLEAN 50 mL Erlenmeyer flask (this is the reaction flask) with the glass tubing set-up which is already prepared. Invert a 10-mL graduated cylinder (filled with water) with your thumb over the top, into a 600 mL beaker which is 2/3 full of room temperature water.

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Procedure “A” is the standard and should be run twice.

versus H-O-O-H 203

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Complete the following table of the rates of reaction of catalase (the enzyme) with hydrogen peroxide (the substrate). Exp part

Specific reaction conditions

Volume of oxygen collected

A)

Standard (35ºC and 15 drops)

A) _______________

A)

Standard (2nd run)

A) _______________

B)

Decrease H2O2

B) _______________

C)

Decrease temp (0ºC)

C) _______________

D)

Increase temp (100ºC then 35ºC)

D) _______________

E)

pH change

E) _______________

F)

Different substrate

F) _______________

Express in fraction form the ratio of Volume A/Volume B. Express in fraction form the ratio of drops of substrate in A/drops of substrate in B. How do the fractions compare?

Compare the volume of O2 collected at 0ºC to the standard (35ºC) Explain the difference.

After the catalase solution was heated to 100ºC then the reaction was run at 35ºC, what happened to the rate of the reaction? Why?

Did the appearance of the enzyme solution change when it was heated? How did it change? What property of the enzyme was responsible for the change?

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