Lab Report Exercise 9: The Digestive System
To get an idea about the variety of modifications those exist in the organs of the digestive system, and to understand the mechanism of digestion in detail.
Activity 1: Microscopic Observation of Digestive Structures
|Surrounds lumen of the GI tract, consists of lamina propria and epithelial cell layer. Participates in secretion, absorption and protection.|
|It’s moderately dense irregular connective tissue which consists of a network of blood vessels, lymphatic vessels, ganglion neurons (Meissner’s plexus) with white adipose tissue. It assists in nutrition and protection both activities.|
|It is composed of three layers of smooth muscles, nerve network and ganglion neurons (Auerbach’s plexus). It takes part in mixing of the ingested food with gastric juices so that, digestion can occur. It also propels the gastric contents into the small intestine.|
Serosa or Advantitia
|Simple squamous epithelium – mesothelium, small quantity of loose connective tissue, white adipose tissue, large blood vessels, lymphatic vessels, and nerve trunks all can be identified in this structure. It participates in reduction of friction, and also in anchoring as well as protection of the surrounded organs.|
A. Compare the columnar epithelium from the stomach to that of the duodenum. How is each modified to carry out a specific function?
Stomach’s epithelium is composed of two types of cells: goblet and oxyntic. Goblet cells take part in production of mucus that protects the mucosal membrane from the corrosive impacts of HCl (aq) created by the oxyntic cells. Mucus participates in lubrication of food down the canal, and acid generated by it can be credited for favorable pH conditions required for digestion of protein and destruction of harmful bacteria. On the other hand, duodenum membrane generates only some mucus for the purpose of lubrication of food.
B. What are the structural modifications you saw in the salivary glands that allow them to carry out their function?
Large size of parotid gland can be termed as; a favorable feature for its wrapping around the mandibular ramus, and for secretion of saliva through Stensen’s ducts into the oral cavity. Besides, sub-mandibular gland consists of the sub-mandibular duct with the help of which it can empty its contents at target site.
C. Where can you find Kupffer cells and what do they do?
Kupffer cells can be found in liver as; these line the walls of the sinusoids and participate in the formation of Reticulo Endothelial System (RES). These cells also remove debris from the blood thus; can be called quite valuable constituents of body.
- How is the ileum structurally different from the duodenum?
Duodenum is the first part of small intestine through which entry of food occurs in the stomach while, ileum is the second part of intestine. Duodenum consists of leafy-looking villi which can be called histologically exclusive structures. Besides, Brunner’s glands that take part in secretion of mucus can also be found in the duodenum only whereas; ileum is a long structure that contains vastly folded surface composed of villi. These assist in absorption of terminal products of digestion.
E. What is the alimentary canal?
Alimentary canal might be defined as; the passage (involving the esophagus, stomach, and intestines) along which food can be passed through the body from mouth to anus.
Activity 4: Digestive enzymes and Physiology
|Data Table 1 : Carbohydrate Digestion|
|Tube||Observations (Glucose Test)|
|1. Amylase, Cracker, 37 degree C||Positive (fast reaction)|
|2. Amylase, Cracker, 22 degree C||Positive (slow reaction)|
|3. Distilled Water, Cracker, 37 degree C||Negative|
|4. Distilled Water, Cracker, 22 degree C||Negative|
|Data Table 2 : Protein Digestion|
|1. Trypsin, BAPNA, 37oC||Cleavage of the substrate (BAPNA) in fast manner|
|2. Trypsin, Distilled Water, 37oC||No Reaction only dissolution of Trypsin in water (fast)|
|3. Trypsin, BAPNA, 22oC||Cleavage of the substrate in slow manner|
|4. Trypsin, Distilled Water, 22oC||No Reaction only dissolution of Trypsin in water (slow)|
|Data Table 3A : Emulsifications and Controls|
|1. Oil and Water||No Emulsification|
|2. Oil, Water and Bile Salts||Emulsification present (Conversion of fat into smaller particles)|
|3. Pancreatin and Distilled Water (Control)||No color change|
|4. Phenolphthalein, cream solution and
Distilled Water (Control)
|No color change|
|Data Table 3 B : Record the relative color of the test tubes
(Compare to control Test Tubes 5 and 6).
|Minutes||Test Tube 1||Test Tube 2||Test Tube 3||Test Tube 4
|Lighter than test tube 6, but not than test tube 5||Reflects color resemblance with test tubes 5 and 6||Lighter than both test tubes 5 and 6||Lighter than test tube 6, but not than test tube 5|
|Lighter than test tube 5 too||Lighter than test tube 6 but not than 5||Lighter than before||Lighter than test tube 5 too|
|Lighter than before||Lighter than test tube 5 now||Lighter than before||Lighter than before|
|Lighter than before||Lighter than before||White||Lighter than before|
|Lighter than before||Lighter than before||White||White|
|White||Lighter than before||White||White|
- What is hydrolysis?
Hydrolysis means; disintegration of a chemical compound through reaction with water.
- Complete the following table:
|Organ Producing it||Site of Action||What does it work on? (Substrate)||Optimal pH|
|Salivary amylase||Salivary glands||Mouth||Starch||Neutral|
How does BAPNA work?
This is used to identify the activity of Trypsin, a pancreatic enzyme that can take part in hydrolysis of proteins. In fact, BAPNA is a synthetic dye which is covalently bonded to an amino acid. Its solution is usually colorless, but can be turned yellow owing to hydrolysis. Because of similarity between the covalent bond found in BAPNA as of the covalent bonds present between amino acids within a protein, there could be observed a positive hydrolysis reaction which might indicate that bond present between the dye and the amino acid in BAPNA could be separated due to activity of Trypsin.
- You ran both a body temperature and room temperature test for each enzyme you tested. Did the two temperatures seem to have an effect on the enzyme activity? Why or why not?
Yes, there might be identified considerable difference between activities shown by enzyme at different temperatures. The key reason behind is that enzymes are proteinaceous by nature the configuration of which might be transformed significantly at variable temperature conditions. Besides, temperature might also impact the interaction present between/among substrate and enzyme molecules thus; highest activity of enzyme can be recognized at that temperature where amino acids present in it are in best configurational state in context of interaction with each other and of course, with substrate moieties.
- Why did you have control tubes in each experiment?
Control tubes assist us in diagnosis of experimental faults via providing the opportunity of comparative analysis.
F. Explain how salivary amylase works on foods like crackers?
Salivary amylase can digest the starch through catalyzing the hydrolysis procedure because of which, starch can be converted into maltose.
- Explain how Trypsin works on proteins?
Trypsin might split the molecules and can also work with Caroxy-Polypeptidase and Proclastase for the purpose of breaking down of the elastin fibers present in the protein structure.
- Fat digestion requires two steps? What are the steps and what enzymes are used to accomplish each?
Emulsification of fats can occur into smaller globules through bile produced by the liver.
Lipids might be broken down into their constituent materials via enzymes such as; lipase.
Summarize Objectives/answer hypothesis/big pictures
●● Identify the organs of the digestive system and relate structure to function.
- ● Observe the microscopic structure of various digestive structures and relate tissue structure and function.
● Explain the process of digestion and how enzymes work to digest food particles.
Digestion means; conversion of macromolecules into micro-ones to ease the process of absorption and further energy-production. Enzymes might break the bonds present in polymer molecules and thus; can convert them into their monomeric units for instance; pepsin can convert protein into amino acids.
●● Relate how specific enzymes work to digest carbohydrates, proteins, lipids, and nucleic acids.
All enzymes work on same principle that is; conversion of macro molecules into micro molecules through breakage of bonds, and promotion of biochemical reactions via reduction of activation energy required initiating the same.