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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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