Name: ____________________________________
Digestion Enzymes: Graphing Activity
Date: ________________ Hour:____
PART I: A scientist performed an experiment to determine the amount of time needed to digest protein. He placed small pieces of
hard-boiled egg white (a protein) in a test tube containing hydrochloric acid, water, and the enzyme pepsin. He measured the rate at
which the egg white was digested over a 24-hour period. His data are recorded in the graph.
Analysis:
1. What do the values on the y-axis represent?____________________________________
2. What is the independent variable?___________________________________________
3. Which axis contains the independent variable?_________________________________
4. What is the dependent variable?____________________________________________
5. After how many hours would you estimate that half of the protein was digested?_______
6. How much digestion occurred in 16 hours? ________________________________
7. During which four-hour period did the most digestion take place?___________________
8. Using the graph can you determine the rate that carbohydrates were digested? ________
9. Using your knowledge of digestion, where would protein digestion begin?_____________________________
Be completed?____________________________________
PART II: Base your answers to questions 7 and 12 on the information and data table below as well as your knowledge of the
digestive system.
The effect of temperature on the action of pepsin, a protein-digesting enzyme present in stomach fluid, was tested. In
this investigation 20 milliliters of stomach fluid and 10 grams of protein were placed in each of five test tubes. The tubes
were then kept at different temperatures. After 24 hours, the contents of each tube were tested to determine the amount
of protein that had been digested. The results are shown in the table below:
Protein Digestion at Different Temperatures:
Tube #
Temperature (0C)
Amount of Protein Digested (grams)
1
5
0.5
2
10
1.0
3
20
4.0
4
37
9.5
5
85
0.0
10. Using the information in the data table, construct a line graph on the graph paper provided.
Following these directions:
a. Make the appropriate scale on each axis.
b. Plot the data on the grid
c. Connect each point to form a line
d. Label each axis
e. Title your graph
11. _____The dependent variable in this investigation is the:
a. Size of the test tube
c. amount of stomach fluid
b. Time of digestion
d. amount of protein digested
Name: ____________________________________
Digestion Enzymes: Graphing Activity
Date: ________________ Hour:____
12. _____The independent variable in this investigation is the:
a. Size of the test tube
c. amount of stomach fluid
b. Time of digestion
d. amount of protein digested
13. _____The control of this experiment:
a. Size of the test tube
b. Time of digestion
c. amount of stomach fluid
d. amount of protein digested
14. _____If a sixth test tube identical to the other tubes was kept at a temperature of 30 0C for 24 hours, the amount of protein
digested would most likely be:
a. Less than 1.0 gram
c. Between 4.0 and 9.0 grams
b. Between 1.0 and 4.0 grams
d. More than 9.0 grams
15. This investigation was repeated using 10 grams of starch instead of protein in each test tube. The contents of each tube were
tested to determine the amount of starch that had been digested. The test results showed that no starch digestion occurred.
Explain why no starch was digested:______________________________________________________________________
____________________________________________________________________________________________________
____________________________________________________________________________________________________
Part III:
Carla’s mother told her that she should chew her food well before swallowing it. Carla’s mother said, “Carla, chewing your food
well will digest it and make less problems in your gut.” Carla did not believe her mother. She decided to do an experiment to find out
for herself. Carla took 10 equal sized pieces of bread. Carla took the first piece of bread and put it on a saucer labelled “0”. She put a
few drops of iodine on the bread. The iodine immediately turned a dark blue-black color. Carla knew from her science class that this
meant that the bread contained starch. She then chewed the second piece for 5 seconds (she timed herself using a stopwatch) and spat
it onto a saucer labelled “5 secs”. She then put a few drops of iodine on the chewed bread. The brown color iodine turned blue-black
immediately. Carla then chewed the third piece of bread for 10 seconds, and repeated the procedure with the iodine. She continued in
this way until she chewed the last piece for 45 seconds. The iodine stayed brown and only a spot here or there turned blue black very
slowly. She looked at her results and particularly at the amount of blue-black colouration on each sample. She estimated a percentage
of blue-black stain for each sample and called this the percentage of starch left in the bread. She drew up the following table:
Time in seconds
% starch left
0
100
5
80
10
60
15
40
20
30
25
22
30
16
35
14
40
12
45
12
Analysis:
1. Draw a line graph of these results on the attached sheet of graph paper.
Following these directions:
a. Make the appropriate scale on each axis.
b. Plot the data on the grid
c. Connect each point to form a line
d. Label each axis
e. Title your graph
2. From the graph, determine what percentage of starch remains if the bread is chewed for 8 seconds. ________________________
3. How long should Carla chew if she wants 18% of the starch left in the bread? _____________
4. Was Carla’s mother correct? Explain your answer._________________________________________________________________
____________________________________________________________________________________________________________
____________________________________________________________________________________________________________
5. Do you think the same results would have been obtained if Carla chewed meat and tested for protein? ____________________
Explain your answer. ________________________________________________________________________________________
___________________________________________________________________________________________________________
____________________________________________________________________________________________________________