The actual energy is not directly in the form of ATP usage, but rather from what is known as the Proton Motive Force. In this case, energy from the Proton Motive Force is used for flagellum rotation instead of for the synthesis of ATP - which simply means a net loss of potential ATP available for other processes - therefore - the use of ATP. This force is generated when hydrogen ions (protons) are generated and extruded to the outside of the cell during electron transport (electrons have come from the "burning" of sugar nutrient - protons come along with the electrons). The build-up of this positive charge on the outside of the cell creates a voltage gradient analogous to water pressure. As the protons re-enter the cell through special molecules, the dissipation of the voltage potential across the membrane releases energy - which can be used to synthesize ATP or in this case, to rotate the flagellum. An analogy would be that of opening the water tap, and using the water pressure to turn a wheel.
people.ku.edu
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Rhetoric to the rescue.
Exceptions aren't just rhetoric.
A theory that covers all general cases may turn out to be trivial. It is the investigation of the boundaries of the theory that reveal it strength. Another famous and well studied theory is that of the Panda's thumb. Darwin's theory of descent with modification would lead one to predict that a Panda would have 5 digits, just like it's nearest relatives and practicly all terrapods, but a Panda has 5 fingers and a thumb.
In short, the fossils of Panda ancestors had 5 digits and they evolved to cluster together as 5 fingers. This is an arrangement suitible for digging or tearing at decayed trees or something. As Pandas began to incorporate more bamboo in their diet they would apparently use their paws to move the branches toward their mouth. The Proto-pandas that did this well had lumpier wrists, which helped guide the bamboo shoots. This evolved further until the Pandas of today have what appears as a thumb, but it is supported by the bones that other terrapods use as part of the wrist movement.
The exception showed that descent with modification explains the unusual as well as the typical. |
