FREE ESSAY ON ELECTRON TRANSPORT

ELECTRON TRANSPORT

Electron Transport Essay 
Electron transport is the last phase and most important phase of cell respiration. It
accounts for most of the ATP made in cell respiration. Cell respiration makes a total of
thirty eight ATP's, two from Glycolysis, two from the Krebs cycle and thirty four from
electron transports. Electron transport takes place after Glycolysis and the Krebs cycle.
Glycolysis and the Krebs cycle make their ATP through substrate level Phosphorylation
while electron transport makes its ATP through oxidative phosphorylation. Glycolysis and
the Krebs cycle are important to electron transport; NADH carries electrons from
glycolysis to the spot where electron transport takes place. NADH and FADH2 carry the
electrons from the Krebs cycle to the spot of electron transport. So with out Glycolysis
or the Krebs cycle electron transport would not take place. 
The electron transport chain is located in the inner membrane of the mitochondrion. It is
made up of a collection of molecules that are set up in a way that each molecule is less
electronegative than the molecule below it. So like a set of stairs as you go down the
stairs each molecule becomes more electronegative and then when you get to the second to
last step if you have ever heard the saying, that last step is a big one you could use
that phase in this context. The last step is from a relatively low electronegative
molecule to a oxygen molecule which has a very high electro negativity. Most components
of the chain are proteins. Tightly bound to these proteins are prosthetic groups,
nonprotein essential for the catalytic functions of certain enzymes. During electron
transport along the chain, these prosthetic groups alternate between reduced and oxidized
states as they accept and donate electrons. Each member of the chain changes between a
reduced state and an oxidized state. A component of the chain becomes reduced when it
accepts electrons from its above stair (which has a lower affinity for the elections).
Each member of the chain returns to its oxidized form as it passes electrons to the stair
lower than it (which has a higher affinity for electrons) does. At the bottom is oxygen,
the overall energy for electrons travailing from NADH to oxygen is 53 kcal/mol, but this
fall is broken up in to a series of small steps by the electron transport chain. 
Most of the ATP made from electron transport is from the electrons transported by the
NADH from Glycolysis. There is another thing that adds to the amount of ATP that electron
transport is the FADH2 from the Krebs cycle. FADH2 carries electrons from the Krebs cycle
to the electron transport chain. It drops its electrons off at the third stair of the
chain. The electron transport chain makes about one third less with FADH2 as the electron
donor. 
The electron transport chain makes no ATP directly. Its function is to ease the fall of
electrons from food to oxygen, breaking a large free energy drop into a series of smaller
steps that release energy in manageable amounts. The mitochondrion couple this electron
transport and energy release to ATP synthesis this is called cheiosmosis. Populating the
inner membrane of the mitochondria are many copies of the protein complex ATP synthase,
this is the enzyme that actually makes ATP. It works like an ion pump but in the opposite
direction. If you remember right on ion pump uses ATP as the energy source to run the
pump. In the reverse of that process, an ATP synthase uses the energy of an existing ion
gradient to power ATP synthase. The ion gradiant that drives oxidative phosphorylation is
a proton gradient; that is, the power source for the ATP synthase is a difference in the
concentration of protons on opposite sides of the inner mitochondrial membrane. We can
also think of this gradient as a difference in pH, since pH is a measure of proton
concentration. The chain is an energy converter that uses the exergonic flow of electrons
to pump hydrogen across the membrane, from the matrix into the inter membrane space. The
Hydrogen ions leak back across the membrane, diffusing down its gradient. But the ATP
synthase, are the only patches of the membrane that are freely permeable to hydrogen
ions. The complex of proteins functions as a mill that harnesses the exergonic flow of
hydrogen ions to drive the phosphorylation of ADP. Thus, an hydrogen ion gradient couples
the redox reactions of the electron transport chain to ATP synthesis. This coupling
mechanism for oxidative phosphorylation is called chemiosmosis a term that highlights the
relationship between chemical reactions and transport across a membrane.