BIOL 207: Lab 11
NAME:
SECTION DAY & TIME:
BIOL 207 LAB 11: Digestion
Results & Questions
Ex. 11.1: Gastric Digestion (from pp. 11.1-11.2)
1. Complete the table below.
Color after addition of
pH Biuret reagent
Tube 1 (pepsin + albumin) 4 violet
Tube 2 (HCl + albumin) 2 Dark purple
Tube 3 (gastric juice + albumin) 2 pink
2. a) Based on the colors, which of these tubes had the greatest amount of protein breakdown?
Tube 3 had the most amount of protein digestion
b) Why did this particular tube have the greatest amount of protein breakdown? (i.e. What
necessary components did it have?)
Since the pH is 2, that means it did have hydrochloric acid in the test tube and we also had pepsin in the test
tube.
3. What are the three roles of HCl and the role of pepsin in the breakdown of proteins in the
stomach? Parietal cells, found in the fundus of the stomach, secrete HCl. HCl is needed to create a
low pH in the stomach for the optimal activity of pepsin. HCl also aids in the conversion of
pepsinogen to pepsin. Furthermore HCl helps pepsin by denaturing proteins that will be digested by
pepsin. Denaturation makes the peptide bonds more available to pepsin. The role of pepsin in the
stomach is to digest proteins through breaking peptide bonds.
4. If a protein is denatured,
a) are the secondary and tertiary structures altered? YES
b) is the primary structure altered? NO
11.1
, BIOL 207: Lab 11
Ex. 11.2A: Intestinal Digestion –Digestion of Starch by a Pancreatic Enzyme (from pp. 11.2)
5. Complete the table below. NOTE: Sometimes the starch solution is too concentrated to be
sufficiently digested in the provided time frame, so if your results were atypical, also indicate
the expected color.
Observed color after Expected color after the
pH addition of iodine addition of iodine
Tube 1 (starch + pancreatic solution) 7.4 Yellow yellow
Tube 2 (starch + water) 6.8 Teal Dark
Tube 3 (starch + boiled pancreatic solution) 7.4 blue blue
6. a) Which of your tubes should have lost the most starch?____TUBE 1
c) EXPLAIN the expected result by describing what conditions should cause the reaction to
work or not work for EACH of the 3 tubes.
Test tube #1 lost the most starch due to the pancreatic solution. In the pancreatic solution there
is amylase, an enzyme that breaks down carbohydrates, making the pancreatic solution break
down the starch.
Test tube #2 did not contain any pancreatic solution and there were no enzymes to break down
the starch, serving as the control in the experiment.
Test tube #3 contained boiled pancreatic solution, denaturing the enzymes.
7. a) What is the general biochemical reaction for starch digestion?
Starch + water O Amylase O Maltose
Label the substrates and products.
The substrates are starch and water and the product is maltose.
8. a) What is the name of the enzyme in the pancreatic solution that is responsible for
the breakdown of starch? Amylase
11.2
NAME:
SECTION DAY & TIME:
BIOL 207 LAB 11: Digestion
Results & Questions
Ex. 11.1: Gastric Digestion (from pp. 11.1-11.2)
1. Complete the table below.
Color after addition of
pH Biuret reagent
Tube 1 (pepsin + albumin) 4 violet
Tube 2 (HCl + albumin) 2 Dark purple
Tube 3 (gastric juice + albumin) 2 pink
2. a) Based on the colors, which of these tubes had the greatest amount of protein breakdown?
Tube 3 had the most amount of protein digestion
b) Why did this particular tube have the greatest amount of protein breakdown? (i.e. What
necessary components did it have?)
Since the pH is 2, that means it did have hydrochloric acid in the test tube and we also had pepsin in the test
tube.
3. What are the three roles of HCl and the role of pepsin in the breakdown of proteins in the
stomach? Parietal cells, found in the fundus of the stomach, secrete HCl. HCl is needed to create a
low pH in the stomach for the optimal activity of pepsin. HCl also aids in the conversion of
pepsinogen to pepsin. Furthermore HCl helps pepsin by denaturing proteins that will be digested by
pepsin. Denaturation makes the peptide bonds more available to pepsin. The role of pepsin in the
stomach is to digest proteins through breaking peptide bonds.
4. If a protein is denatured,
a) are the secondary and tertiary structures altered? YES
b) is the primary structure altered? NO
11.1
, BIOL 207: Lab 11
Ex. 11.2A: Intestinal Digestion –Digestion of Starch by a Pancreatic Enzyme (from pp. 11.2)
5. Complete the table below. NOTE: Sometimes the starch solution is too concentrated to be
sufficiently digested in the provided time frame, so if your results were atypical, also indicate
the expected color.
Observed color after Expected color after the
pH addition of iodine addition of iodine
Tube 1 (starch + pancreatic solution) 7.4 Yellow yellow
Tube 2 (starch + water) 6.8 Teal Dark
Tube 3 (starch + boiled pancreatic solution) 7.4 blue blue
6. a) Which of your tubes should have lost the most starch?____TUBE 1
c) EXPLAIN the expected result by describing what conditions should cause the reaction to
work or not work for EACH of the 3 tubes.
Test tube #1 lost the most starch due to the pancreatic solution. In the pancreatic solution there
is amylase, an enzyme that breaks down carbohydrates, making the pancreatic solution break
down the starch.
Test tube #2 did not contain any pancreatic solution and there were no enzymes to break down
the starch, serving as the control in the experiment.
Test tube #3 contained boiled pancreatic solution, denaturing the enzymes.
7. a) What is the general biochemical reaction for starch digestion?
Starch + water O Amylase O Maltose
Label the substrates and products.
The substrates are starch and water and the product is maltose.
8. a) What is the name of the enzyme in the pancreatic solution that is responsible for
the breakdown of starch? Amylase
11.2
