BIOL 204 Lab 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:
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
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?
Activity 1 Trypsin Activity Trypsin an enzyme, secreted by pancreatic acinar cells, that hydrolyzes proteins into small fragments (peptones, peptides and proteoses)”
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?
Starch + H2O maltose (disaccharides) 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 Fatty Acids + Glycerol
Fat Digestion: Indicator: Blue litmus turns pink (red) in the presence of acid (one the products is fatty acids)
Bile emulsifies fat….
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
Gastroesophageal Junction ACTIVITY 4 Gastroesophageal Junction Gastric pit
Microscopic anatomy of the stomach.
Intestinal Villus Duodenum
Liver Microscopic Anatomy
Microscopic View of the Pancreas: Islet Cells: endocrine; secrete insulin and glucagon into bloodstream Acinar Cells: exocrine; secrete digestive enzymes into pancreatic duct