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 + H 2 O 1. N-benzoyl-L-arginine + p-nitroaniline (yellow) Reaction rate will be compared at these different incubation temperatures: 370 C and 0 o 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 + H 2 O 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: 0 o. C and 37 o. C

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 + H 2 O 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 (0 o. C vs. 37 o. C) and addition of bile salts on the reaction

Activity 4 Gastroesophageal Junction Different microscopic views

Histology of The Stomach Wall

Histology of the Small Intestine (Duodenum) Micrograph

Intestinal Villus

Liver – Microscopic Anatomy

Microscopic View of the Pancreas: Islet Cells: endocrine; secrete insulin and glucagon Acinar Cells: exocrine; secrete digestive enzymes