High School Biology-Chemistry SMILE Meeting
05 March 2002
Notes Prepared by Porter Johnson

Karlene Joseph (Lane Tech HS) -- Gas Laws
first showed a diagram that allows us to determine how electrons fill atomic orbitals, from lower energy to higher energy:

Sub-shells (# electrons)Atomic Number
for Full Sub-shell 
11s2  2
22s2 2p6  4   10
33s2 3p6 3d1012   18   30
44s2 4p6 4d10 4f1420   36   48   68
55s2 5p6 5d10 5f1438   54   78 102
66s2 6p6 6d1012   84 112 
73s2 7p6 86 118

The filled P-subshells occur for noble gases:  Z= 2 (Helium), 10 (Neon), 18 (Argon), 36 (Krypton), 54 (Xenon), 84 (Radon), and 118 (żż Valium ??).  It appears as though atoms with atomic number of 118 are at about the limit of discovery.

Karlene next considered the role of oxygen in cellular respiration.  She began by posing these three questions:

How long can humans live without food? .......... Perhaps 2-3 weeks
How long can humans live without water? Perhaps 2-3 days
How long can humans live without oxygen? Perhaps 5 minutes
So why is oxygen so important?  Because of its role in cellular respiration.  Cellular respiration [http://www.ultranet.com/~jkimball/BiologyPages/C/CellularRespiration.html] is summarized in the following equation:
C6H1206 ® 6 H20 + 6 C02 + energy
We then looked at a diagram of a cell [http://www.ultranet.com/~jkimball/BiologyPages/A/AnimalCell.gif], focusing in on mitochondria -- bean-shaped organelles with "squiggles", the squiggles being folds of an inner membrane system.  Cellular respiration begins in the cytosol (the space outside organelles and the cell nucleus) through the reaction known as glycosis, in which glucose is split into two Pyruvic Acid molecules.
C6H1206 ® 2 C3H403 + 4H (eventually ionized)
Pyruvic Acid then diffuses into the mitochondria. Inside the mitochondria, Pyruvic Acid is eventually converted into carbon dioxide and other products through a biochemical pathway known as the Krebs Cycle.  In this process, as well as in glycosis, ATP [Adenosine TriPhosphate] is produced.  ATP is the chemical produced and used to store energy within cells, and the energy is released in small amounts through release of a phosphate ion P04---
ATP (Adenosine TriPhosphate) ® ADP (Adenosine DiPhosphate) + P04--- + energy
Conversely, ATP may be formed from ADP to store energy in cells:
ADP (Adenosine DiPhosphate) + PO4--- + energy ® ATP (Adenosine TriPhosphate)
For each glucose molecule, we have the potential to produce 2 ATP molecules in glycosis and 2 ATP molecules in the Krebs Cycle.  Energy obtained from these processes can also be stored within  NADH [Nicotinamide Adenine Dinucleotide] and FADH2 [Flavin Adenine Dinucleotide] molecules.

Now we come to the topic of electron transport.  The compounds NADH and FADH2 donate high energy electrons to a transport chain in the inner mitochondrial membrane.  As the electrons are passed from one component of the chain to the next, and ultimately to hydrogen ions H and O2 molecules to form water, energy is released and used to pump hydrogen ions H+ from the mitochondrial matrix into the inter-membrane space.  The hydrogen ion then moves back from the region of high concentration [inter-membrane space] to low concentration [matrix] and releases energy.  The energy released in this process is used to form ATP from ADP, thereby storing more energy in the cell.  It is estimated that as many as 34 ATP molecules can be created from the energy in a single glucose molecule by this process of electron transport. Consequently, one can store the energy in a single glucose molecule by creating up to 38 ATP molecules.

Karlene then had us form a (human) electron transport chain, with each person being either part of the electron transport chain (passing electrons on to the next link) or to a second cycle of (human} "oxygens" taking up electrons at the end of the chain and producing water at the same rate as electrons are passing through the chain.  We then reduced the number of "oxygens" by about 60%, so that the electron chain is forced to move more slowly.  If all the "oxygens" sat down, no electron transport could occur, and we would lose the energy stored in 34 ATP's.

Great activity, and great lesson, Karlene!

Notes taken by Ben Stark