1. BIOL 204 Lab
Week 12
Digestive Enzymes

2. 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:

3. Amylase: digests starch into disaccharides
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

4. Variables tested ……
Incubation temperature:
How will enzyme activity compare when incubated at O o C and 37 o C?
Denaturization of Enzymes
How will enzyme activity be altered if the enzyme is denatured by boiling?

5. Activity 1 Trypsin Activity
Trypsin an enzyme, secreted by pancreatic acinar cells, that hydrolyzes proteins into small fragments (peptones, peptides and proteoses)”

6. What do you predict will happen?
In this experiment, trypsin will act on an artificial substrate to yield a yellow colored product:
Trypsin
BAPNA + H2O N-benzoyl-L-arginine + p-nitroaniline (yellow)
1. 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?

7. Starch + H2O maltose (disaccharides)
Activity 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)

8. 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

9. IKI Test For Starch in a Spot Plate
Benedict’s Test for reducing sugar in heat test tubes

10. As in activity one, the reaction will be observed under different conditions:
Boiled Enzyme (Amylase)
Incubation Temperature: 0oC and 37oC

11. 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 Fatty Acids + Glycerol

12. Fat Digestion: Indicator:
Blue litmus turns pink (red) in the presence of acid (one the products is fatty acids)

13. Bile emulsifies fat….

14. incubation temperature (0oC vs. 37oC)
In this activity, you will examine the effect of:
incubation temperature (0oC vs. 37oC)
and
addition of bile salts
on the reaction

16. Gastroesophageal Junction
ACTIVITY 4
Gastroesophageal Junction
Gastric pit

17. Microscopic anatomy of the stomach.

18. Intestinal Villus
Duodenum

19. Liver Microscopic Anatomy

20. Microscopic View of the Pancreas:
Islet Cells: endocrine; secrete insulin and glucagon into bloodstream
Acinar Cells: exocrine; secrete digestive enzymes into pancreatic duct