1.8 Lipids properties

Introduction
Lipids are a heterogeneous 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, phospholipis. terpens and steroids.


Material
-Test tube rack
-250mL beaker
-water
-Test tube rack
-Cellulose paper
-Dropper
-Scissors
-Glass rod
-Olive oil
-Soap (detergent)
-Milk with different fat content: full-cream, semiskimmed, and skimed milk.
-Petroleum ether
-Ethanol
-Sudan III


Objectives 
1. Test the solubility of lipids.
2. Identify lipids in liquids compounds.
3. Understan what are an emulsion ant the effect of detergents.

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

Observations:
-The water inthe first test tube create a monolayer and the ethanol and ethet dissolved.


Lipids identification:
Translucent mark:
7.Cut two pieces (10x10cm) of cellulose paper.
8.Put 1 drop of water in the first squared pices. You will see a transluced spot. Wait for a while and observed what is happening.
9.Put 1 drop of olive oil in thesecond squared pieces ofcellulose paper. You will see a translucent spot. Wait for a while andpbserve what is happening. Has the spot disappeared? Why?


Sudan III dye:
Sudan III is a red fat-soluble dye that is utilized in the identification of 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.Prepared four test tubes: 3 with milk with differents fat content (M1, M2, M3) an soda (S). Add two drops of Sudan III and observe the results.

Observations:
-We can see that the colous of the oil change bacause it hasfatty 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 dropps of soap and stir the mixtue again. Let it stand for a few minutes and notice the differents between both mixture.

Observations:
Water whith olive oil. We can see that whenwe stir the water with oil, the oil never dissolved 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 f¡let the micelles come together.