LIPIDS PROPERTIES

Introduction:
Lipids are heterogenous group of compounds synthesized by organisms that are present in all biological tissues. 
These compounds are characterized as natural substances that do not mix with water but dissolve in organic solvents. 
There are several classes of lipids, including: fatty acids, waxes, triacylglycerols, phospholipids, trepens ans steroids. 

Objectives: 
- Test the solubility of lipids. 
- Identify lipids in liquids compounds. 
- Understand what are an emulsion and the effect of detergents 

Procedure: 
Solubility of some lipids:
1- Clean and dry three test tubes. Label as W (water), ethanol (E) and PE (ether)
2- Add 3 drops of oleic acid to 3 small test tubes. 
3- Add 1 ml of water in the first test tube (W)
4- Add 1 ml of ethanol in the second test tube (E). 
5- Add 1 ml of petroleum ether in the third test tube (PE). 
6- Shake carefully each test tube and record solubility and observations in your worksheet. 

Conclusion: The water in the first test tube create a monolayer, and the ethanol and the ether dissolve. 

Lipids identification: 
Translucent mark:
7- Cut two pieces (10x10) of cellulose paper. 
8- Put 1 drop of water in the first squared piece. You will see a translucent spot, wait for a while and observe what is happening. 
9. Put 1 drop of olive oil in the second squared piece of cellulose paper. You will see a translucent spot. Wait for a while and observe what is happening. Ha the spot disappeared? Why? 

Sudan III dye: 
Sudan III is a red fat-soluble dye that is utilitzed in the identification of the presence of lipids, triglycerides and lipoproteins in liquids. 

10- Take the W test tube of the first experiment and add 2 drops of Sudan III 
11- Prepare four test tubes: 3 with milk with different fat content (M1, M2, M3) and soda (S). Add two drops of Sudan III and observe the results.  

Results: 
We can see that the colour of the oil change (red) because it has fatty acids. The water doesn't change the colour because doesn't have fats.

PERMANENT EMULSION: 
12- Take a 250ml beaker and put 100ml of water. 
13- Add 1ml of olive oil. With a glass rod stir the mixture vigorously and let it stand for a few minutes. 
14- Make note of what is happening. 
15- Add 2 drops of soap and stir the mixture again. Let it stand for a few minutes and notice the differences between both mixtures.

Results: 
Water with oil = We can see that when we stir the water with oil, the oil never dissolve, the micelles come together. 
Water with oil and soap = The micelles are not together because there are soap, and create a membrane that don't let the micelles come together. (We can see in the image).