Biology 2021 Digestive Wet Lab Writeup
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DUE: ______________
Download this document and type your answers to the questions so that your document contains
both questions & answers. Answers must be in complete, grammatically correct sentences.
Attach the results table or retype the results table within the document.
Turn in a HARD COPY of the printed document (with table attached). 10pt font with single
spaced, narrow margin pages is fine.
Name(s):
1. What is the purpose of this experiment? (i.e. What physiological process are we observing?)
In this experiment we’re observing chemical digestion. Specifically, we observed the processes of
chemical digestive of starch through Maltose by salivary Amylase.
2. What is your hypothesis? (Do not state predictions here, which are treatment tube specific)
In this experiment, we will examine how well pH and temperature affect salivary Amylase.
3. Define the term “independent variable” in the context of a scientific experiment. Identify the
independent variable(s) in this experimental set-up.
An independent variable is the part of the experiment that the experimenter changes in order to test
the dependent variable. Thus, the temperature and pH of the enzyme is our independent variable in
this particular experiment.
4. Define the term “dependent variable” in the context of a scientific experiment. Identify the
dependent variable(s) in this experimental set-up.
A dependent variable is the variable that changes in the experiment due to the independent variable.
This is the variable that is affected and measured in the experiment. Thus, the amount of Maltose is
what is measured and observed in this experiment.
5. What are controls and why are they necessary in a scientific experiment? Identify the tube(s) that
served as control(s) for the presence of maltose & explain why.
Controls are the things that stay the same throughout the experiment. They’re necessary in the fact
that they can do a number of things, but in particular, they are something to compare to. This
comparison can be used help find any differences in the dependent variable or emphasize the
change in general. Ultimately, the increase the reliability of the results. Thus, the control in this
experiment would be Tubes 1 & 8. In these tubes we could observe the extremes of both sides of the
experiment. In tube 1 we had no saliva, and just water – resulting in no color change. While in tube 8
we only had Maltose – which would result in major color change.
6. What is the chemical process behind the color change in the tubes in this experiment?
Benedict’s regent is used to reveal the amount of Maltose present in a solution. Specifically,
Benedict’s regent contains the ionic form of copper called the cupric form (Cu+++). When Benedict’s
reagent is mixed with maltose and heated, the maltose “reduces” the cupric ion to the cuprous ion
(Cu+) by donating an electron. This ultimately produces the color change to either green, yellow,
orange, or red.
7. Compare the results in tube 2 with the results in tube 5. Explain the differences seen.
(NOTE: Telling me the colors of the tubes is NOT an explanation.)
In the results of tube 2, which was placed in the warm water bath, the solution contained high
amounts of Maltose. Adversely, Tube 5 contained little to no Maltose. While it also was placed in a
warm water bath, it had 5 drops of HCL that tube 2 didn’t have. Having said that, perhaps the HCL
was what created such a large difference? The severely low pH probably resulted in poorer results.
8. Based on your answer to #7, predict if salivary amylase would work in the stomach if it were to be
found there. Why or why not?
I’d predict that salivary amylase would NOT work in the stomach if it were found there. While tube 2
had no HCL in its solution, the results showed high concentrations of Maltose. And the opposite
results were found in tube 5 while there was HCL in the solution. As a result, that means that salivary
Amylase doesn’t work around stomach acid/ HCL, and thus, it doesn’t work in the stomach.
9. Compare the results in tube 2 with the results in tube 6. Explain the differences seen.
In the results of tube 2, which was placed in the warm water bath, the solution contained high
amounts of Maltose. Adversely, Tube 6 contained little to no Maltose despite being in the same warm
water bath. This is due to the Extremely high pH in the solution from the NaOH.
10. Compare the results in tube 2 with the results in tubes 3 and 4. Explain the differences seen.
In the results of tube 2, which was placed in the warm water bath, the solution contained high
amounts of Maltose. Similarly, in tubes 3 and 4 we could observe substantial concentration despite
being left in extremely cold temperatures and room temperatures.
11. Compare the results in tube 2 with the results in tube 7. Explain the differences seen.
In the results of tube 2, which was placed in the warm water bath, the solution contained high
amounts of Maltose. Contradictory to this, tube 7 is met with little to no Maltose. Perhaps due to the
extreme boiling temperature that was done earlier.
12. Imagine if, after boiling the saliva in tube 7 and adding the starch, we added 5 drops of HCL and
incubated the tube in an ice bath before testing for the presence of maltose. What could we conclude
about those results?
We could most likely conclude that there would absolutely be no Maltose concentration in the
solution. This is because of the results of said solutions beforehand, which were all negative for
Maltose after boiling, freezing, and adding HCL.
13. Based on your data, what are the best conditions for salivary amylase activity in terms of
temperature and pH?
Based on everything given, I’d say that a pH of 7 and simply a warm water bath is the ideal conditions
for salivary amylase activity. Because every extreme seems to severely inhibit the activity.
14. Did you get any unexpected results (anything that did not match your hypothesis or predictions)?
My predictions for tubes 3, 4, 5, and 6 were completely wrong. I initially thought that perhaps Amylase
activity would be increased/ decreased on different factors. While on the 3 rd tube I think I predicted
correctly, it was still wrong because of strong enzymes in the saliva.
15. What is one suggestion you have for improving the results of this experiment?
Perhaps eating more food before the experiment begins. Or waiting longer than an hour for the
solutions to stay in their said environments (pH and temperature environments). Maybe create/ use
another control in the experiment. Maybe people can only eat a certain type of food before the
experiment, or perhaps a certain number of calories. Maybe the control could be gender based, or
weight based? There would be a myriad of things you could change to try and improve results.