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Toxins interfere with mitochondrial function in three ways:

1. Electron Transport Inhibitors

Environmental toxins such as herbicides, insecticides, and fungicides can prevent the passing of electrons by binding to one or more of the proteins that carry electrons. Examples:

  • Insecticide: rotenone 
  • Fungicides: carfboxin, oxycarboxin, and fenfuran 
  • Herbicides: chlorproham, propanil, dinoseb, and ioxynil. 
2.  Uncouplers

Cyanide is a classic poison that prevents the addition of high energy phosphate groups to make the energy storage compound, ATP.  Other well-known compounds that act this way include the pesticides pentachlorophenl (PCP) and 2,4-dinitrophenol (DNP).

3.  Inhibitory Uncouplers

Herbicides may also fall into this category. Some insecticides, such as DDT and cyclodiene, are in this group.

Something to Think About

Part of the way that these toxins act comes from their ability to penetrate and stick in membranes.  Recall that when any large compound gets incorporated in a membrane, it disturbs the position of the other compounds that are normally found there. In the membranes that make up the folds inside of mitochondria, such disturbance interferes with the  passing of electrons that is needed to couple energy to ATP synthesis.

Here is a question to think about: Could herbicides and insecticides affect processes in other membranes, such as those in the nuclear membrane or membranes where proteins are made (endoplasmic reticulum), or even the cell membranes of excitable cells such as nerve cells?

 

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