Tuesday, February 10, 2015

Membrane modelling minilab questions

Phospholipid and cholesterol form membranes due to their having one end called a "head" which is attracted to the polar water, and on the other end are "tails" made of oil chains which are attracted to the nonpolar oil. Phospholipids and similar compounds will form a single "monolayer" membrane around grease, oil, and dirt, by their nonpolar "hydrophobic" tails sticking to the dirt while the water loving "hydrophilic" heads point outward to contact the water.
A phospholipid membrane which forms around a small droplet of water (instead of oil) is called a "Vesicle" which has a phospholipid "bilayer" where instead of a single membrane where all the tails stuck into an oil droplet there is a second inner membrane that has the phospholipid molecules pointing the other way so their heads contact the water droplet on the inside, with the tails of the inner membrane strongly attracted to the tails of the outer membrane which squeezes out anything that tries to come between them.
Vesicles are also very good at trapping such things as RNA and DNA which might end up included in your experiment, especially if you poked through the egg yolk's nucleus when you took the sample.


Analysis Questions:
  • What are the bilayer membranes most like in cell biology?  Monolayer membranes?
  • Describe how this activity is representative of evidence for a possible theory in the origin of life. 
  • Did you notice any of the droplets growing or dividing?  Explain how this might be relevant to the origin of life.
  • What aspects of complete living single cell are missing in this demo?
  • What happened when you added Fe particles?  How might this relate to endosymbiont theory?

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