Exercise 8: Chemical and Physical Processes of Digestion

Topics: Digestion, Enzyme, Starch Pages: 2 (537 words) Published: April 22, 2013
Lab Report 8
April 15th

Exercise 8: Chemical and Physical Processes of Digestion
Lab Report Questions

Activity 1
What is the difference between the IKI assay and Benedict’s assay? IKI assay detects the presence of starch, and the Benedict assay tests for the presence of reducing sugars as well as IKI turns blue black whereas Benedict is a bright blue that changes to green to orange to reddish brown with increasing levels of maltose

What was the purpose of tubes #1 and #2? Why are they important? Because they are the controls and the controls must be prepared to provide a known standard against which all comparisons must be made. Positive controls all of the required substances are included and negative a negative result is expected validating the experiment.

What effect did pH level have on the enzyme?
It partially allowed the enzyme to do its job because there were positive signs of both starch and its reducing sugars.

What effect did boiling and freezing have on the activity of amylase? Boiling did not allow the breakdown of starch because the reduced sugars were not present and the starch was where the freezing showed a ++ for the reducing sugars and a negative result in the starch showing that it reduced the starch.

Activity 2
What was the effect of the enzyme peptidase? Why?
The enzyme peptidase could not break down the starch by showing that there is positive IKI test for starch and a negative Benedict test for its reduced sugars. What is cellulose? According to your results, does salivary amylase digest cellulose? Cellulose is a polysaccharide found in plants to provide rigidity to their cell walls and salivary amylase is not able to digest it because there were no positive signs of the Benedict test which should have been positive if a breakdown did occur.

What happened to the cellulose in tube #6?
It was digested by the bacteria showing a very positive sign for the Benedict test. Activity 3
What is the optimal pH level for...
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