SPEAKER: The center of activity that brings your cells to life
is found inside the dynamic mitochondria organelle.
The inner mitochondrial membrane is
coated with enzymes that catalyze the chemical reactions
of respiration, working in sequence to generate
the electron transport chain.
The first step in the electron transport chain
is performed by enzyme complex 1.
Complex 1 receives electrons from coenzyme NADH,
a substrate produced by the citric acid cycle.
The catalytic mechanism of enzyme complex 1
connects two different kinds of reaction.
Coenzyme NADH is oxidized at one end of the enzyme,
releasing two electrons that hop through the interior
to coenzyme Q, which is reduced.
Traveling amongst membrane lipids,
coenzyme Q carries electrons to the next step in the electron
transport chain.
The movement of charged electrons through complex 1
makes it bend in shape, transmitting energy
for pumping four protons across the membrane.
The second step of the electron transport chain
is performed by enzyme complex 3.
The mechanism of complex 3 separates electrons
from coenzyme Q, passing one electron
to cytochrome c, which is reduced.
A complete reaction cycle of enzyme complex 3
transports four protons across the membrane.
Traveling within the intermembrane space,
reduced cytochrome c carries the electron
to the final step in the electron transport chain.
The destination for electron transport
is a molecule of oxygen held inside enzyme complex four.
Reduced cytochrome c delivers electrons
that transfer to the reaction center of enzyme complex four.
A molecule of oxygen from the air you breathe
is captured, split, and reduced.
The separated oxygen atoms accept electrons
and pick up protons, creating two molecules of water.
The substrate providing electrons to enzyme complex 1
is coenzyme NADH, a product of the citric acid cycle.
A second supply of electrons for the electron transport chain
is from step 6 of the citric acid cycle, performed by enzyme
complex 2.
Enzyme complex 2 catalyzes oxidation of succinate,
releasing two electrons which hop through the enzyme
to coenzyme Q, which is reduced.
Traveling through the membrane, coenzyme Q
carries the electron to enzyme complex 3 of the electron
transport chain.