High School Biology-Chemistry SMILE Meeting
25 February 2003
Notes Prepared by Porter Johnson

Chris Etapa [Gunsaulus Academy]      Diffusion and Osmosis [7th Grade Level]

  1. Chris had filled  a [pint / half-liter] jar to the top with dried beans, then had added as much water as she could to the jar, then had put the lid on the jar, and had let it sit overnight. The water disappeared.  Why?  One reasonable hypothesis is that water had been absorbed into the beans through osmosis, so that the beans should have swelled.  To demonstrate swelling, she took the lid off the jar and inverted it.  The beans did not fall out of the jar, because they had been "squeezed into place".
  2. Chris then had placed the stems of white carnations [celery would also work] into a glass of water to which food coloring [red or blue] had been added.  The colored water could be seen rising up the stem, and then the flowers turned red  or blue.   For celery, we could see the color go up the xylem of the celery, which is visible in that plant.
  3. For the third experiment Chris used a raw egg from which the shell had been dissolved by soaking it in vinegar for a few days.  She first put the shell-less egg in Karo™ Syrup [the clear stuff ---not the kind in pecan pies!].  The egg shrank because of osmosis --- water inside the egg passed through the membrane and went into the syrup. [The same effect occurs with salt water, because the concentration of water is higher inside the egg in both cases.] If a shell-less boiled egg is placed in water, the egg swells, because the concentration of water inside the egg is less than that in the surrounding fluid, so that water travels into the egg through osmosis.  One may easily measure the amount of water that left an egg in syrup, as well as the amount of water that went into the egg in water, either by weighing  the egg or measuring the fluid volumes, before and after.

We continued the discussion concerning the differences of water present in eggs, syrup, and pure water.  We concluded that nature works [sometimes magically and mysteriously!]  to drive processes toward equilibrium. For the egg, the concentration of water inside and outside should become the same through the process of diffusion. Seeds must absorb water [imbibition --- drinking --- vraiment un mot Francaise] before they can sprout. In potatoes, vegetative sprouting of the "eyes" [meristematic tissue --- undifferentiated plant tissue in the process of formation -- Greek meristos / meristos: divided] results in a new potato plant.  See the USDA Biology of the Potato website: http://www.ars.usda.gov/research/publications/publications.htm?seq_no_115=105408

Osmosis practically makes the world go round. Very nice, Chris!

Ken Schug [IIT Chemistry]      Three Presentations from His Bag of Tricks

  1. Ken took a dollar bill  from his hapless victim, Ben Stark, dipped it into an unspecified liquid, held it in his hand, and lit it with a match.  A big flame arose, which Ken blew out by shaking the bill. Ben's bill survived the ordeal intact.  The liquid, which consisted principally of ethyl alcohol, smelled strongly of peppermint.  Then Ken performed the same experiment with his own finger.  He dipped the finger into the liquid, lit it, and then shook out the flame.  Why didn't the bill or his finger get burned?  It was our consensus that alcohol burns at a lower temperature than the ignition temperature of paper --- Fahrenheit 451, according to sci-fi writer/guru Ray Bradbury: http://en.wikipedia.org/wiki/Fahrenheit_451  --- or of fingers, for that matter!
  2. Ken brought out a jar of a clear liquid with dark blobs at the bottom of the jar.  Ken had evidently been trying to make his very own Lava LampHow does a Lava Lamp work?  There is a light bulb just underneath, which generates both light and heat when turned on.  The idea is to have a semi-solid material (wax?) --- one that is not soluble in water ---- which expands with temperature at a greater rate than the bulk liquid.  The semi-solid mass gets near the light /heat source, becomes warmer, expands, and then rises to the cooler region in the vessel, where it becomes more dense, and sinks.

    We then talked about how the fact that the density of water varies with temperature is important in biology --- particularly the fact that water has a maximum density at 4° C.  As a consequence of this fact, no part of a body of water [lake or pond] can sustain a temperature below 4° C unless and until temperature of the entire body of water is reduced to 4° C.  Further cooling at the top results in a temperature inversion, at which the top layers of water are cooler than those near the bottom, and an ice layer forms on the top of the body of water.  Fish and other organisms can survive in the cold, but unfrozen water beneath the ice layer. 
  3. Ken initiated a discussion of proteins by asking the following questions:
    There is a myriad of ways of polymerizing these 20 amino acids in distinct combinations to form a virtually endless variety of protein structures. Proteins are "biological polymers", in the same sense that plastics are "non-biological polymers".

    Ken illustrated the process of polymerization using starch, which is a polymer consisting of units of glucose.  There are various enzymes that de-polymerize starch, converting it into glucose, so that it can be digested.  Ken pointed out that cellulose is also a polymer with glucose units, but the glucose units are connected differently in starch and in cellulose.  We cannot digest cellulose, although certain organisms (e.g. certain fungi and bacteria) can digest it.

    How many different proteins be assembled from just 20 different amino acids?  Ken illustrated the combinatorial possibilities using hookable beads of  5 different colors.  For ordered polymers consisting of 10 units --- dekamers, or whatever --- there are 105 different color combinations.  One may assemble 4 beads of different colors into 24 = 4 ´  3 ´  2 ´  1 distinct ways, whereas 5 beads of different colors can be assembled in 120 distinct ways.  For protein pentamers --- or 5 unit polymers --- there are 205 = 3,200,000 different possibilities.  Real polymers consist of around 100 to 1000 amino acids, so that there is a virtually limitless set of possibilities --- 20100 is comparable to the number of hydrogen atoms in the universe!

We continued to discuss topics such as protein structure, Recombinant DNA, and genetic engineering.  In particular, we discussed the number of different proteins present in a given organism.  That number can be as small as 484 in the simplest bacterium, whereas in humans there are 35,000 - 40,000 different types of protein.

New tricks from old dogs came forth in abundance! Great job, Ken!

Scheduled Future Presentations:

Notes taken by Ben Stark.