Introduction to Experiment 2: Protein Digestion by PepsinIn this experiment, we will look at for evidence of protein digestion using albumin, a protein, and Biuret reagent. Biuret reagent is used to test for the presence of proteins, or more specifically, peptide bonds. When long polypeptide chains are present the solution will turn violet, and when shorter polypeptide chains are present the solution will turn a lighter pink color.What is/are the end product(s) of protein digestion? Amino acidsWhat is the purpose of the enzyme pepsin? It helps in the digestion of proteins by breaking down the peptide bonds between amino acids into smaller peptidesIf protein digestion has occurred, will the solution be violet or pink (choose one)?Hypotheses/Predictions (See Methods section for details): What color do you expect the solution to turn when the P tubes are mixed with Biuret solution and why?P1 P2 P3 P4 The least protein digestion (or none at all) will take place in tubes (P1, P2, P3, and/or P4)? Why? What color will these tubes be after the Biuret test? Of the remaining two tubes, tube ________ will have more protein digestion than tube _________.Why? Introduction to Experiment 3: Lipid Digestion by LipaseIn this experiment, we will investigate lipid digestion. Remember that lipids include fats, so the two terms are often used interchangeably. To do this, we will use litmus cream, which is a mixture of cream and litmus. Cream contains triglycerides (neutral fats). Litmus is a pH indicator. Purple indicates a neutral pH. Pink indicates an acidic pH. Blue indicates a basic pH. How do bile salts act on a mixture of fat and water?What is/are the end product(s) of fat digestion? Is either of these end products acidic? If so, which one? _Hypotheses/Predictions (See Methods section for details): :Which of the tubes do you expect will have the most digestion of fats? The next most digestion of fats? No digestion of fats? Explain.Rank the tubes in order of predicted acidity at the end of the experiment. Most Acidic Least AcidicTubenumber What color do you expect each tube to be after the hour long incubation period?L3 L4 L5 RESULTS Experiment 1: Starch Digestion by AmylaseTube numberA1A2A3A4Contentsamylase, water Lugol’s Solution test result (color) Positive (+) or Negative (-) for starch digestion N/A, control N/A, control N/A, control Benedict’s Reagent test result (color) Positive (+) or Negative (-) for starch digestion N/A, control N/A, control N/A, control Other comments or possible errors? Experiment 2: Protein Digestion by PepsinTube numberP1P2P3P4Contentsalbumin, water pH before incubation Color after Incubation Positive (+) or Negative (-)for protein digestion N/A, control Other comments or possible errors? Experiment 3: Lipid Digestion by LipaseTube numberL1L2L3L4L5Tube contentsLitmus cream, HCl Color after incubation (color is an indicator of pH) Positive (+) or Negative (-) for fat digestion? N/A, control N/A, control N/A, control Other comments or possible errors? DISCUSSIONExperiment 1: Starch Digestion by AmylaseThe purpose of test tubes A2 and A3 is to illustrate what a positive result looks like for Lugol’s solution and Benedict’s reagent. Did these tubes appear how you expected them to appear? If not, what might this mean? What was the purpose of test tube A1? (Hint: review or look up the definition of an experimental control.) Describe the results of tube A4. Are the results of test tube A4 when mixed with Lugol’s solution and with Benedict’s reagent consistent with what you know about starch digestion by amylase? Which of your hypotheses were correct? Incorrect? Explain the results that caused you to reject incorrect hypotheses, if you made any. List some possible experimental errors that may have influenced your results.Experiment 2: Protein Digestion by PepsinWhat was the purpose of tubes P1 and P2?Does the effectiveness of pepsin depend on pH? Explain, using your results.Which of your hypotheses was correct? Which were incorrect?Are the results of this experiment consistent with what you know about pepsin?List some possible experimental errors that may have influenced your results.Experiment 3: Lipid Digestion by LipaseIn this experiment, you observed the pH of the solutions, as indicated by their final color. How can the pH of a solution tell you if fat digestion has occurred? (Hint: refer to the questions you answered in the introduction.)Which of your hypotheses were supported by the results? Which were not?What was the purpose of test tubes L1, L2 and L3?List some possible experimental errors that may have influenced your results.

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Biochemistry

9th Edition

ISBN:9781319114671

Author:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.

Publisher:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.

Chapter1: Biochemistry: An Evolving Science

Section: Chapter Questions

Problem 1P

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Question

Introduction to Experiment 2: Protein Digestion by Pepsin

In this experiment, we will look at for evidence of protein digestion using albumin, a protein, and Biuret reagent. Biuret reagent is used to test for the presence of proteins, or more specifically, peptide bonds. When long polypeptide chains are present the solution will turn violet, and when shorter polypeptide chains are present the solution will turn a lighter pink color.

What is/are the end product(s) of protein digestion? Amino acids
What is the purpose of the enzyme pepsin? It helps in the digestion of proteins by breaking down the peptide bonds between amino acids into smaller peptides
If protein digestion has occurred, will the solution be violet or pink (choose one)?

Hypotheses/Predictions (See Methods section for details):

What color do you expect the solution to turn when the P tubes are mixed with Biuret solution and why?

The least protein digestion (or none at all) will take place in tubes (P1, P2, P3, and/or P4)?

Why?

What color will these tubes be after the Biuret test?

Of the remaining two tubes, tube ________ will have more protein digestion than tube _________.

Why?

Introduction to Experiment 3: Lipid Digestion by Lipase

In this experiment, we will investigate lipid digestion. Remember that lipids include fats, so the two terms are often used interchangeably. To do this, we will use litmus cream, which is a mixture of cream and litmus. Cream contains triglycerides (neutral fats). Litmus is a pH indicator. Purple indicates a neutral pH. Pink indicates an acidic pH. Blue indicates a basic pH.

How do bile salts act on a mixture of fat and water?

What is/are the end product(s) of fat digestion?
Is either of these end products acidic? If so, which one? _

Hypotheses/Predictions (See Methods section for details): :

Which of the tubes do you expect will have the most digestion of fats? The next most digestion of fats? No digestion of fats? Explain.

Rank the tubes in order of predicted acidity at the end of the experiment.

Most Acidic

Least Acidic

Tube

number

What color do you expect each tube to be after the hour long incubation period?

RESULTS

Experiment 1: Starch Digestion by Amylase

Tube number	A1	A2	A3	A4
Contents	amylase, water
Lugol’s Solution test result (color)
Positive (+) or Negative (-) for starch digestion	N/A, control	N/A, control	N/A, control
Benedict’s Reagent test result (color)
Positive (+) or Negative (-) for starch digestion	N/A, control	N/A, control	N/A, control
Other comments or possible errors?

Experiment 2: Protein Digestion by Pepsin

Tube number	P1	P2	P3	P4
Contents	albumin, water
pH before incubation
Color after Incubation
Positive (+) or Negative (-)for protein digestion	N/A, control
Other comments or possible errors?

Experiment 3: Lipid Digestion by Lipase

Tube number	L1	L2	L3	L4	L5
Tube contents	Litmus cream, HCl
Color after incubation (color is an indicator of pH)
Positive (+) or Negative (-) for fat digestion?	N/A, control	N/A, control	N/A, control
Other comments or possible errors?

DISCUSSION

Experiment 1: Starch Digestion by Amylase

The purpose of test tubes A2 and A3 is to illustrate what a positive result looks like for Lugol’s solution and Benedict’s reagent. Did these tubes appear how you expected them to appear? If not, what might this mean?

What was the purpose of test tube A1? (Hint: review or look up the definition of an experimental control.)

Describe the results of tube A4. Are the results of test tube A4 when mixed with Lugol’s solution and with Benedict’s reagent consistent with what you know about starch digestion by amylase?

Which of your hypotheses were correct? Incorrect? Explain the results that caused you to reject incorrect hypotheses, if you made any.

List some possible experimental errors that may have influenced your results.

Experiment 2: Protein Digestion by Pepsin

What was the purpose of tubes P1 and P2?

Does the effectiveness of pepsin depend on pH? Explain, using your results.

Which of your hypotheses was correct? Which were incorrect?

Are the results of this experiment consistent with what you know about pepsin?

List some possible experimental errors that may have influenced your results.

Experiment 3: Lipid Digestion by Lipase

In this experiment, you observed the pH of the solutions, as indicated by their final color. How can the pH of a solution tell you if fat digestion has occurred? (Hint: refer to the questions you answered in the introduction.)
Which of your hypotheses were supported by the results? Which were not?
What was the purpose of test tubes L1, L2 and L3?