BIO132 Lab 7:
Exercise 39A/39 Chemical Processes of Digestion
Digestion = hydrolysis reactions involving enzymes
(enzymes = biological catalysts)
-a specific enzyme acts on a specific substrate using water to break
chemical bonds resulting in particular products
-the specificity is based on the active site of the enzyme; a space in
folded protein structure where the substrate will fit and bind
-enzymes are usually named for their substrate and end in “-ase”
Figure 39A.1 / 39.1
Cofactor
Lipid emulsification by bile
(mix)
Fats and oils + bile --------------------------> emulsified fats
(tiny droplets suspended in water)
allows easier access by water-soluble enzymes
Figure 39A.1 / 39.1
*NOT digestion!
Enzymes are biological catalysts, proteins that function to “speed up”
chemical reactions by holding substrate in the active site.
Enzymatic reactions can be impacted by environmental conditions:
-Enzymes have optimal temperatures and pH for their activity.
-Human digestive enzymes have an optimal temperature equal to body
temperature (37°C). Most have an optimal pH around neutral (pH7)
-If the temperature is too high, or pH is too acidic or basic, enzymes can
be denatured and will no longer catalyze the reaction.
-If the temperature is too low, enzymes will function slowly or not at all
in the reaction.
Salivary Amylase Digestion of Starch
Tube no.
1A
2A
3A
4A
6A
37°C
0°C
Add acid
Boil amylase
4 min, then
add starch
Additives
(3 gtt ea)
Incubation
condition
5A
37°C
37°C
37°C
37°C
IKI test
(color change)
Positive (+) or
negative (-)
result
Benedict’s
test
(color change)
Positive (+) or
negative (-)
result
native conformation
Additive key:
denatured
Amy Warenda Czura, Ph.D.
= Amylase
1
= Starch
= Maltose
= Water
SCCC BIO132 Lab 7 Digestion
Unnumbered Figure 39.3
Salivary Amylase Digestion of Starch
Tube no.
1A
2A
3A
4A
5A
6A
Pancreatic Lipase Digestion of Fats
Add acid
Boil amylase
4 min, then
add starch
Additives
(3 gtt ea)
Incubation
condition
37°C
IKI test
(color change)
yellow black yellow
37°C
37°C
37°C
37°C
yellow
-
+
-
+
Benedict’s
test
(color change)
blue
blue
orange
blue
Positive (+) or
negative (-)
result
-
-
+
-
dark
2L
3L
4L
5L
4B
5B
37°C
0°C
37°C
0°C
Boil lipase
4 min, then
15
add litmus
cream.
Incubation
condition
37°C
37°C
37°C
Color change
partial +
Positive (+) or
negative (-)
result
orange yellowish
+
1L
Additives
(5 gtt ea)
0°C
black
-
Positive (+) or
negative (-)
result
Tube no.
Additive key:
partial +
= Lipase
= Litmus cream
= Water
= Pinch bile salts
Additive key:
= Amylase
= Starch
= Maltose
= Water
Pancreatic Lipase Digestion of Fats
Tube no.
1L
3L
2L
4L
5L
4B
5B
37°C
0°C
37°C
0°C
Boil lipase
4 min, then
15
Additives
(5 gtt ea)
add litmus
cream.
Incubation
condition
37°C
Color change
Positive (+) or
negative (-)
result
37°C
37°C
bluish bluish
purple purple
-
bright pinkish
bluish purple
pink purple pink purple
-
++ -/+ +++ +
-
Additive key:
= Lipase
= Litmus cream
= Water
= Pinch bile salts
Amy Warenda Czura, Ph.D.
2
SCCC BIO132 Lab 7 Digestion