Mitochondria uncoupling

Laties and associates589-592 provided evidence for an alternative, cyanide-resistant path of respiration in avocado mitochondria. Uncouplers were considered to stimulate glycolysis to the point where the glycolytic flux exceeds the oxidative capacity of the cytochrome pathway, with the result that the alternative pathway is engaged. However, these authors concluded that the alternative pathway is not required in order to sustain the elevated rate of respiration that characterizes the climacteric. Clarification of the role, if any, of this alternative pathway in fruit ripening awaits further study. 

Agents that uncouple oxidative phosphorylation in mitochondria uncouple photoelectron transport and ATP formation in photosynthesis. Explain. 

Maintenance of respiratory control depends on the structural integrity of the mitochondrion. Disruption of the organelle causes electron transport to become uncoupled from ATP synthesis. Under these conditions, oxygen uptake proceeds at high rates under all conditions. ATP synthesis is inhibited, even though electrons are being passed along the respiratory chain and used to reduce 02 to water. 

In other words, in the absence of O2 this cytochrome will be kept almost completely in the reduced form in an uncoupled mitochondrion. 

Chemical uncouplers can also influence cell fate other than through depletion of ATP [153, 154] and their action to depolarize membranes outside of the mitochondrion also needs to be considered with respect to their overall effects on the target cell or organism for instance, they have been shown to dissipate plasma membrane potential and to destabilize lyzosomes [155, 156]. 

To explain these two stages in mitochondrial swelling, it has been proposed that the mitochondrion can be described as a structure made of two concentric compartments. Without thyroxine or another swelling agent, only the outside compartment is permeable to sucrose, but when thyroxine is added to the medium, the second compartment also becomes permeable to sucrose. During swelling, the NAD bound to the mitochondrial structure is progressively lost, and oxidation is uncoupled from phosphorylation. 

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