Biomedical Engineering Reference
In-Depth Information
hand, several experimental findings are against this hypothesis, for example, it could not
account for the uncoupling of electron transfer system and phosphorylation system in the
presence of uncoupling agents.
Heat
Mechanical
functions
Energy
source
AT P
Catabolism
Maintenance
Anabolism
ADP+Pi
Figure 3. The role of the ATP-ADP cycle in cell metabolic system. During catabolism, energy
transformation occurs from energy source. Some portion of the produced energy (in the form of ATP)
will be utilized in mechanical functions, maintenance and anabolism, while some portion of energy will
be lost in the form of heat.
O
O
O
+
H
+
OH
ROP
O
P
O
OP
O
O
O
ADP
Pi
O
O
O
ROP
O
P
O
P
O
+
H
2
O
O
O
O
ATP
Figure 4. The scheme of ATP synthesis process [51].
2. The Conformational Coupling Hypothesis
This popular hypothesis was first put forward by Paul Boyer in 1964, stating that electron
transport generates energized proteins with activated conformations, when interacting with
ATP synthase, it will relax back to deactivated states and drive ATP synthesis. This
hypothesis eventually evolved into the binding change mechanism in 1970s on the basis of
detailed kinetic and binding studies of the reactions catalyzed by F
0
F
1
and finally
complemented by Boyer with rotational catalysis in 1990s. Two possibilities have been
