Drawing Hydrophobic and Hydrophilic Interactions Worksheet KEY:
Worksheet KEY:
1. Emulsifiers surround oil and form a protective layer so that the oil molecules cannot "clump" together. This action helps keeps small droplets dispersed in an aqueous (watery) environment. This is similar to what happens when you use soap to wash oil from a pan. Thinking about the properties of lipids and water, what properties would your emulsifier need to have? Draw the basic structure of your emulsifier. Then, draw your emulsifier surrounding the oil droplets in a water environment. Compare and discuss this with your classmates. Did you come up with a similar design?
I draw the analogy that an emulsifier would need to be able to interact with two friends that can’t get along — like a mediator. So, one end would need to be hydrophobic and one end would need to be hydrophilic. Students then come to the conclusion that it is amphiphilic like they have learned about phospholipids. I bring up some examples of student drawings that get at these points.
2. What class of biological lipids has properties much like the emulsifiers? Phospholipids
3. During the BP oil spill of 2010 in the Gulf of Mexico, why was the dispersant/emulsifier, Corexit applied to the waters? What would this have accomplished? (Over 800,000 gallons of dispersants had been applied to Gulf waters mainly via helicopter, but also includes 100,000 gallons that were injected deep underwater.)
The dispersants caused the oil to be “dispersed” and some of it settled into deeper water.
Many students are not informed about this aspect of the oil spill and are surprised to find out that this was a strategy employed by BP. Students are interested to learn that the oil might be hidden but not gone and that the dispersant itself might be toxic.
4. Lipids are an excellent source of energy in your diet. Yet your internal environment is aqueous. How do you think lipids enter into the cells of your gut, given their hydrophobic properties?
Because lipids like oils conglomerate, an emulsifier (bile) is needed to keep these oil droplets dispersed. This allows lipase to break the macromolecules into monomers. Monomers are absorbed through the intestinal cells. I often explain that this dish detergent works in a similar fashion too, by being a mediator between oil and water while they wash dishes.
5. Going back to your structural design of emulsifers, how would your picture change if you had a few droplets of water dispersed in an oily environment with the help of an emulsifier? Reverse of picture above.