The ETS reactions are oxidation-reduction (Redox)
reactions. During the transfer of hydrogen/electrons through the
chain, each carrier molecule is alternately reduced and oxidized.
For example, when a carrier accepts hydrogen/electron it gets reduced.
On the other hand, the reduced carrier is oxidized when it transfers
the hydrogen/electron to the next carrier in the chain.
There is a net flow of electrons through the ETS
from more electronegative redox potential (i.e. from NADH2
or FADH2) to the more electropositive redox potential
(i.e. to oxygen).
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Overall result of aerobic respiration
Complete oxidation of one molecule of 6-C glucose
through aerobic respiration (involving glycolysis, Kreb’s cycle,
ETS, etc.) results in —
(a) release of 6#CO2
(b) Utilization of 6#O2 and
(c) Formation of 6#H2O.
However, 6H2O are used up in Kreb’s
cycle (involving 2 pyruvic acid molecules).
\ 12 H2O formed - 6H2O
used = 6H2O net gain