Lesson
Purpose of the work:
– experimentally familiarize with the process of emulsifying fats
Run time: minutes
Expected results
After studying the project, students will be able to:
- develop teamwork skills
- be able to analyze and summarize the information received
- draw logical conclusions
- use practical skills in studying the process of emulsifying fats
Teacher’s guide:
- Divide the students so that there are 3 students in each group.
- Before starting laboratory work, please read the safety rules by following the link:
To download the worksheet, follow the link:
Theoretical part
Bile is the secretion of the liver, the largest gland in the human body. In the human body, 700-800 g of bile is formed per day, which accumulates in the gallbladder, and then is released into the intestine to participate in digestion. The composition of bile includes: water (97-98%), bile acids (67%), bile pigment – bilirubin (0.3%), cholesterol (4%).
One of the main functions of bile is to emulsify fats. Emulsification is the process of breaking large fat droplets into small particles. When fats enter the small intestine during digestion, bile is released from the gallbladder and mixed with the ingested food. Bile contains bile acids, phospholipids, and other substances. Bile acids are the key components responsible for emulsification.
The bile acids in the bile interact with the fat molecules, forming small droplets called micelles. These micelles have a unique structure where the hydrophobic (fat-loving) parts of the bile acids face inward, surrounding the fat molecules, while the hydrophilic (water-loving) parts face outward, interacting with the surrounding watery environment.
This arrangement of the micelles increases the surface area of the fat, exposing more fat molecules to the action of digestive enzymes called lipases. Lipases break down the fat molecules into smaller components, such as fatty acids and glycerol, which can be easily absorbed by the body.
Experimental part
In addition to the bile acids produced in the body, fat-dissolving emulsifiers include protein, soap solution, and alkaline solution. Let’s find out the effectiveness of these substances in practice.
Step 1. Place 5 clean test tubes on a rack and number them. Using a pipette, pour 2 drops of vegetable oil and 1 ml of water into each test tube.
Step 2. Add 5 drops of emulsifiers into each tube in turn:
No. 1-alkaline solution
No. 2-bile juice
No. 3-soap solution
No. 4-protein
No. 5-water
Step 3. Shake the tubes for 1 minute until the solutions are mixed.
What changes have taken place?
Step 4. Monitor the stability of the emulsion after 5 minutes.Use a magnifying glass to see the drops of fat. Pay attention to their size.
Step 5. Record the results in a table.
№ | Emulsifier type | Observed changes | |
| After shaking | After 5 minutes | ||
| 1 | Alkaline solution | ||
| 2 | Bile juice | ||
| 3 | Soap solution | ||
| 4 | Egg white | ||
| 5 | Water | ||
Step 6. Drawing conclusions, write down in your worksheet the answers to the following questions:
• Which test tube had large drops of fat observed, and which had smaller ones?
• Based on the experiment, which emulsifier gave the most stable emulsion?
• Summing up the experiment, describe the role of bile in the digestive process.
Conclusion
In this laboratory work, students learned about the importance and function of bile acids in the body. In addition, they received practical skills in studying the process of fat emulsification. We are sure that the acquired new knowledge and skills will be used in the next lessons.
