Oxidative Phosphorylation
We now move our discussion past complexes I-IV on to complex V, called
oxidative phosphorylation, in which ATP is synthesized from ADP and
phosphate in the matrix of the mitochondria. The enzyme that catalyzes this
reaction is called proton translocating ATP synthase the protein component
of complex V.
As we introduced in the last
section, as a
result of the electron transport chain, an electrochemical gradient is
formed on either side of the inner mitochondrial membrane. The outside of the
membrane is positive while the inside is negative. The positive hydrogen ions
are allowed to flow back across the membrane through specialized channels manned
by proton translocating ATP synthase, which uses the energy created by the
energetically favorable transport to synthesize ADP and phosphate into ATP.
Figure 3.1: Oxidative Phosphorylation
The transport of just two electrons through the electron transport chain
generates enough free energy in the form of electrochemical gradient to drive
the synthesis of one molecule of ATP. The synthesis of ATP necessitates the
dissolution of the electrochemical gradient, however, since the whole process is
driven by positive hydrogen ions (protons) flowing back into the matrix space
from the intermembrane space. The ETC maintains the electrochemical gradient by
continuing to generate hydrogen ions.
In total, the process started through the glycolysis of one glucose molecule
yields about 32 ATP in oxidative phosphorylation. In total, oxidative
phosphorylation accounts for around 90 percent of the body's total ATP.
Conclusion
We have now concluded our study of cell respiration, following the entire
process of a glucose molecule from the cytosol and
glycolysis into the mitochondria and
through the electron transport chain and oxidative phosphorylation. With our
new knowledge, we can now produce an updated version of our overall map of cell
metabolism.
Figure 3.2: Map of Cell Metabolism
