Interrelationship between oxidative energy transformation and energy consumption at mitochondrial and cellular levels.

The adaptation of oxidative energy transformation in mitochondria to the energy demand of cellular metabolism was investigated in experiments with isolated mitochondria and liver cells and by computer simulation in terms of a mathematical model. Separate draining of different energy pools allowed the determination of the relation between these pools and the elucidation of the importance of the connecting enzyme reactions to the regulation of the whole process. The following conclusions can be drawn from the results: 1. The intramitochondrial adenine nucleotide pool exhibits a homogeneous behaviour, and its changes are the signal for ATP synthesis. 2. The proton-motive force which is in near-equilibrium with the intramitochondrial phosphorylation potential is the immediate signal for the respiratory chain. 3. The intramitochondrial phosphorylation potential is transformed into the external one by a flux-dependent non-equilibrium reaction of the translocator. 4. The rate of respiration-linked ATP formation is regulated by more than one reaction step with varying control strength. 5. In both isolated mitochondria and hepatocytes an activation of respiration is provoked by a decrease in the mitochondrial energy state caused by cellular energy utilization.