Nonlinearity of the Flux/Force Relationship in Respiring Mitochondria as a Possible Consequence of Heterogeneity of Mitochondrial Preparations
It is well recognized since early studies on oxidative phosphorylation1,2 that ADP greatly stimulates mitochondrial respiration. This reflects a tight coupling between electron transport and ATP synthesis. Nevertheless, in the absence of added ADP or after its complete phosphorylation to ATP, mitochondrial respiration does not come to a stop but continues at a low, though measurable, level designated as state 4 2 or the resting state. This respiration may be partly attributed to external ATPase and/or recycling of Ca2+. However, even if production of ATP or its exit from mitochondria is blocked and the uptake of Ca2+ is prevented, there still remains a significant oxygen uptake. In terms of the chemiosmotic theory of energy coupling,3 this resting state respiration can be interpreted as compensating the proton leak through the inner mitochondrial membrane.
KeywordsMitochondrial Respiration Proton Leak Respiratory Control Ratio Carbonyl Cyanide Mitochondrial Preparation
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