High School Biology-Chemistry SMILE Meeting
25 February 2003
Notes Prepared by Porter Johnson
Chris Etapa [Gunsaulus Academy]
Diffusion and Osmosis [7th Grade Level]
- 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
- 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
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.
- For the third experiment Chris used a raw egg from which
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: divided] results in a new potato plant. See the USDA
Biology of the Potato website: http://collections.ic.gc.ca/potato/scitech/biology.asp
Osmosis practically makes the world go round. Very nice, Chris!
Ken Schug [IIT Chemistry] Three
Presentations from His Bag of Tricks
- 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
--- or of fingers, for that matter!
- 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
Lamp! How 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
- 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".
- What are proteins and where are they found? [muscles, enzymes, etc]
- What are amino acids? [They are the sub-units or building blocks that are
assembled to make proteins --- all proteins on earth are made from only 20 different
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:
- March 09: Barbara Pawela, Tyrethis Penrice, Chris Clausing, and Christine Scott
- April 08: Carol Giles
Notes taken by Ben Stark.