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THE ELECTRON TRANSPORT
CHAIN
Thus far in aerobic respiration, the glucose has
been broken down, and CO2 has been released. The
electrons removed as hydrogen atoms from the original
glucose molecule are now present as part of ten
NADH and two FADH2 molecules (two NADH from glycolysis;
two NADH from the formation of acetyl-CoA; six
NADH and two FADH2 from the citric acid cycle).
During electron transport, these
NADH and FADH2 molecules are transferred along
a series of acceptors. As the high-energy electrons
are passed from one acceptor to another, some
of their energy is used to synthesize ATP.
The final electron acceptor
in the electron transport chain is oxygen, which
is reduced to water when it accepts two electrons
from the electron transport system and two protons
from the surrounding medium. Altogether, 12 molecules
of H2O are produced from each molecule of glucose.
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