Question

Many potent toxins and lethal poisons exert their effects by interfering with energy production in the cell. Select any such molecule (that interferes with energy production), and discuss which metabolic pathway it affects, particularly which enzyme(s) and how. -----> PLEASE TYPE 250 WORDS & INCLUDE 1 - 2 SOURCES, NO DIAGRAMS

Answer 1

ETS (Electron Transport System) inhibitors act by binding somewhere on the electron transport chain, literally preventing electrons from being passed from one carrier to the next. They all act specifically, that is, each inhibitor binds a particular carrier or complex in the ETS.

Irreversible inhibition results in a complete stoppage of respiration via the blocked pathway. Competitive inhibition allows some oxygen consumption since a trickle of electrons can still pass through the blocked site. Although it allows some oxygen consumption, competitive inhibition prevents maintenance of a chemiosmotic gradient, thus the addition of ADP can have no effect on respiration.

Cyanide is a chemical compound that contains monovalent combining group CN. This group consists of a carbon atom triple - bonded to a nitrogen atom. Cyanide is considered to be toxic because it binds to cytochrome c oxidase ie. the fourth complex in the electron transport chain. It attaches to the iron within this protein complex and inhibits the normal activity of the complex system.

It binds tightly so that it cannot transport any electrons to oxygen. This blocks the further passage of electrons throughout the chain, halting ATP production. Since no ATP is made, the electron transport chain stops working. This is so because the protons are not allowed to go back into the matrix of the mitochondria, thus, the concentration of protons build up and the gradient becomes large.

Therefore, the person is deprived of chemical energy to perform the many numerous processes that sustain life and the person dies.

References:

1. Beasley, D.M.G. and Glass, W.I. Cyanide poisoning: pathophysiology and treatment recommendations. Occup. Med. Vol. 48, No. 7, pp. 427-431, 1998