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
Hydrophilic
would need to be able
Water molecule
to interact with two
Fat molecule
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.
Hydrophobic
Dispersant,
(emulsifier/detergent)
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.