The energy released from the rupture of chemical bonds in food molecules is stored temporarily in the form of high energy electrons in two types of molecule, N and F, whose proportions vary depending on the nutrient source. By themselves, these molecules cannot provide a freely utilizable source of rapidly mobilized energy for the cell's needs; access to this stored energy requires the mitochondria, which uses five molecular machines, called complexes I, II, III, IV and V, to convert the energy stored in N and F molecules into the universal energy source ATP. Until very recently these complexes were thought to float freely and independently in the internal membrane of mitochondria, without interacting. Work by Dr. Enriquez's group has now shown this view to be incorrect. “The five complexes do not always move independently in the membrane,” explains Dr. Enríquez. “On the contrary, they associate in distinct combinations called respiratory supercomplexes. Our work explains the functional consequences of these interactions.” The study shows that these associations are dynamic and are modified to optimize the extraction of energy from N and F molecules depending on their relative abundance, which in turn reflects the composition of foods consumed in the diet. The Science study describes these supercomplexes and their functions. The significance of this, in the words of Dr. Enriquez, is that “the system for optimizing the extraction of energy from food molecules is much more versatile than was believed and can be modulated in unexpected ways in order to adjust to the dietary composition of nutrients or to the specialized function of particular cell types.”
During the study the team also made the unexpected discovery that the most widely used mouse strain for laboratory genetic analysis is unable to correctly assemble the respiratory supercomplexes. This raises serious questions about the validity of extrapolating results obtained with these mice to humans.
More here. (Note: The last paragraph is why I vehemently oppose the use of mouse models to study human cancers)