Once the NADH has been made from a metabolite in the citric acid cycle inside of the mitochondria, it interacts with the first complex 1 enzyme, known as NADH reductase. This complex 1 contains a coenzyme flavin mononucleotide (FMN) which is similar to FAD. The sequence of events is that the NADH, plus another hydrogen ion enter the enzyme complex and pass along the 2 hydrogen ions, ultimately to an interspace in the mitochondria. These hydrogen ions, acting as a pump, are utilized by ATP synthetase to produce an ATP for every two hydrogen ions produced. Three complexes (1, 3, 4) act in this manner to produce 2 hydrogen ions each, and thus will produce 3 ATP for every use of the complete electron transport chain. In addition, NADH passes along 2 electrons to first FMN, then to an iron-sulfur protein (FeS), and finally to coenzyme Q. The net effect of these reactions are to regenerate coenzyme NAD+. This regeneration of reactants occurs in many of the reactions so that a cycling effect occurs. The NAD+ is ready to react further with metabolites in the citric acid cycle. Coenzyme Q, which also picks up an additional 2 hydrogen ions to make CoQH2. Coenzyme QH2 carrying an extra 2 electrons and 2 hydrogen ions now starts a cascade of events through enzyme complex 3, also known as cytochrome reductase bc. Cytochromes are very similar to the structure of myoglobin or hemoglobin. The significant feature is the heme structure containing the iron ions, initially in the +3 state and changed to the +2 state by the addition of an electron. The CoQH2 passes along the 2 electrons first to cytochrome b1 heme, then b2 heme , then to an iron-sulfur protein, then to cytochrome c1, and finally to cytochrome c. In the meantime the 2 hydrogen ions are channeled to the interspace of the mitochondria for ultimate conversion into ATP. Cytochrome c is a small molecule which is also able to move in the lipid membrane layer and diffuses toward cytochrome a complex 4. At this time it continues the transport of the electrons, and provides the third and final time that 2 hydrogen ions are channeled to the interspace of the mitochondria for ultimate conversion into ATP. ATP synthetase (complex 5) is also found at numerous locations in the bilayer membrane of the mitochondria. Three ATP are produced by the pumping action of the re-entry of the hydrogen ions through the ATP synthetase. Finally, oxygen has diffused into the cell and the mitochondria for the finally reaction of metabolism. Oxygen atom reacts with the 2 electrons and 2 hydrogens to produce a water molecule. In summary, the electron transport chain is coupled with the formation of ATP. The coupled reaction may be written as: a) O2 + 3H2 + NAD+ ---> 2NADH + H2O + energy b) ADP + P + energy ---> ATP + H2O Aka, energy produced from A can be coupled to reaction B to produce ATP, this coupling is provided by ATP synthase. Also FADH2 could be implemented into these equations. Solution Once the NADH has been made from .

1. Once the NADH has been made from a metabolite in the citric acid cycle inside of the
mitochondria, it interacts with the first complex 1 enzyme, known as NADH reductase. This
complex 1 contains a coenzyme flavin mononucleotide (FMN) which is similar to FAD.
The sequence of events is that the NADH, plus another hydrogen ion enter the enzyme complex
and pass along the 2 hydrogen ions, ultimately to an interspace in the mitochondria. These
hydrogen ions, acting as a pump, are utilized by ATP synthetase to produce an ATP for every
two hydrogen ions produced. Three complexes (1, 3, 4) act in this manner to produce 2 hydrogen
ions each, and thus will produce 3 ATP for every use of the complete electron transport chain.
In addition, NADH passes along 2 electrons to first FMN, then to an iron-sulfur protein (FeS),
and finally to coenzyme Q. The net effect of these reactions are to regenerate coenzyme NAD+.
This regeneration of reactants occurs in many of the reactions so that a cycling effect occurs. The
NAD+ is ready to react further with metabolites in the citric acid cycle.
Coenzyme Q, which also picks up an additional 2 hydrogen ions to make CoQH2. Coenzyme
QH2 carrying an extra 2 electrons and 2 hydrogen ions now starts a cascade of events through
enzyme complex 3, also known as cytochrome reductase bc.
Cytochromes are very similar to the structure of myoglobin or hemoglobin. The significant
feature is the heme structure containing the iron ions, initially in the +3 state and changed to the
+2 state by the addition of an electron. The CoQH2 passes along the 2 electrons first to
cytochrome b1 heme, then b2 heme , then to an iron-sulfur protein, then to cytochrome c1, and
finally to cytochrome c.
In the meantime the 2 hydrogen ions are channeled to the interspace of the mitochondria for
ultimate conversion into ATP.
Cytochrome c is a small molecule which is also able to move in the lipid membrane layer and
diffuses toward cytochrome a complex 4.
At this time it continues the transport of the electrons, and provides the third and final time that 2
hydrogen ions are channeled to the interspace of the mitochondria for ultimate conversion into
ATP.
ATP synthetase (complex 5) is also found at numerous locations in the bilayer membrane of the
mitochondria. Three ATP are produced by the pumping action of the re-entry of the hydrogen
ions through the ATP synthetase.
Finally, oxygen has diffused into the cell and the mitochondria for the finally reaction of
metabolism. Oxygen atom reacts with the 2 electrons and 2 hydrogens to produce a water

2. molecule.
In summary, the electron transport chain is coupled with the formation of ATP. The coupled
reaction may be written as:
a) O2 + 3H2 + NAD+ ---> 2NADH + H2O + energy
b) ADP + P + energy ---> ATP + H2O
Aka, energy produced from A can be coupled to reaction B to produce ATP, this coupling is
provided by ATP synthase. Also FADH2 could be implemented into these equations.
Solution
Once the NADH has been made from a metabolite in the citric acid cycle inside of the
mitochondria, it interacts with the first complex 1 enzyme, known as NADH reductase. This
complex 1 contains a coenzyme flavin mononucleotide (FMN) which is similar to FAD.
The sequence of events is that the NADH, plus another hydrogen ion enter the enzyme complex
and pass along the 2 hydrogen ions, ultimately to an interspace in the mitochondria. These
hydrogen ions, acting as a pump, are utilized by ATP synthetase to produce an ATP for every
two hydrogen ions produced. Three complexes (1, 3, 4) act in this manner to produce 2 hydrogen
ions each, and thus will produce 3 ATP for every use of the complete electron transport chain.
In addition, NADH passes along 2 electrons to first FMN, then to an iron-sulfur protein (FeS),
and finally to coenzyme Q. The net effect of these reactions are to regenerate coenzyme NAD+.
This regeneration of reactants occurs in many of the reactions so that a cycling effect occurs. The
NAD+ is ready to react further with metabolites in the citric acid cycle.
Coenzyme Q, which also picks up an additional 2 hydrogen ions to make CoQH2. Coenzyme
QH2 carrying an extra 2 electrons and 2 hydrogen ions now starts a cascade of events through
enzyme complex 3, also known as cytochrome reductase bc.
Cytochromes are very similar to the structure of myoglobin or hemoglobin. The significant
feature is the heme structure containing the iron ions, initially in the +3 state and changed to the
+2 state by the addition of an electron. The CoQH2 passes along the 2 electrons first to
cytochrome b1 heme, then b2 heme , then to an iron-sulfur protein, then to cytochrome c1, and
finally to cytochrome c.

3. In the meantime the 2 hydrogen ions are channeled to the interspace of the mitochondria for
ultimate conversion into ATP.
Cytochrome c is a small molecule which is also able to move in the lipid membrane layer and
diffuses toward cytochrome a complex 4.
At this time it continues the transport of the electrons, and provides the third and final time that 2
hydrogen ions are channeled to the interspace of the mitochondria for ultimate conversion into
ATP.
ATP synthetase (complex 5) is also found at numerous locations in the bilayer membrane of the
mitochondria. Three ATP are produced by the pumping action of the re-entry of the hydrogen
ions through the ATP synthetase.
Finally, oxygen has diffused into the cell and the mitochondria for the finally reaction of
metabolism. Oxygen atom reacts with the 2 electrons and 2 hydrogens to produce a water
molecule.
In summary, the electron transport chain is coupled with the formation of ATP. The coupled
reaction may be written as:
a) O2 + 3H2 + NAD+ ---> 2NADH + H2O + energy
b) ADP + P + energy ---> ATP + H2O
Aka, energy produced from A can be coupled to reaction B to produce ATP, this coupling is
provided by ATP synthase. Also FADH2 could be implemented into these equations.