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BIOL 204 Lab For Week 12
Digestive Enzymes
Digestive Enzymes:
are used in the lumen of the GI tract to break down complex
molecules into absorbable subunits
Enzymes are biological catalysts which increase the rate of a
chemical reaction without themselves becoming part of the product:
In this experiment we will observe the activity of three
different enzymes:
Amylase:
digests starch into disaccharides
Trypsin:
digests proteins into peptides
Lipase:
digests fats into glycerol and fatty acids
Variables tested ……
1. Incubation temperature:
How will enzyme activity compare when incubated at O o C and
37 o C?
2. Denaturization of Enzymes
How will enzyme activity be altered if the enzyme is denatured by
boiling?
Activity 1
Trypsin Activity
Trypsin an enzyme, secreted by pancreatic acinar cells,
that hydrolyzes proteins into small fragments (peptones,
peptides and proteoses)”
In this experiment, trypsin will act on an artificial
substrate to yield a yellow colored product:
Trypsin
BAPNA + H2O
1.
N-benzoyl-L-arginine + p-nitroaniline
(yellow)
Reaction rate will be compared at these different incubation
temperatures:
370 C and 0o C
What do you predict will happen?
2.
The rate of the reaction will be determined using boiled
trypsin. What do you predict will happen?
Activity 2
Amylase Activity
Amylase is a carbohydrate digesting enzyme, produced by
salivary glands and pancreatic acinar cells, that hydrolyzes
starch into maltose (disaccharides):
Amylase
Starch + H2O
maltose (disaccharides)
Indicators:
Starch: IKI (Lugol’s solution) -
turns “blue/black” in the
presence of starch
Benedict’s Solution:
turns green/orange/ red/brown
in the presence of reducing sugar
IKI Test For Starch in a
Spot Plate
Benedict’s Test for
reducing sugar in heat
test tubes
As in activity one, the reaction will be observed under
different conditions:
Boiled Enzyme (Amylase)
Incubation Temperature: 0oC and 37oC
Activity 3
Lipase Activity
Lipase is a hydrolytic enzyme, made primarily by pancreatic
acinar cells, that hydrolyzes neutral fats into fatty acids and
glycerol:
Lipase
Fat +
H2O
Glycerol + Fatty Acids
Fat Digestion:
Indicator:
Blue litmus terns pink (red) in
the presence of acid (one the
products is fatty acids)
Bile emulsifies fat….
In this activity, you will examine the effect of:
incubation temperature (0oC vs. 37oC)
and
addition of bile salts
on the reaction