How does Cyanide block the electron transport system?

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Cyanide is a potent inhibitor of the electron transport chain in mitochondria, primarily affecting cytochrome oxidase, which is crucial for oxygen consumption. A concentration of 1 mM KCN can reduce oxygen consumption by over 98%, effectively halting the Krebs cycle, similar to suffocation. This mechanism is akin to carbon monoxide poisoning, where both substances competitively inhibit oxygen binding, but cyanide specifically targets mitochondrial enzymes. The discussion suggests that the effects of cyanide on organisms capable of fermentation could provide further insights into its impact on respiration without oxygen.
ambzrose
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How do deadly chemicals like Cyanide, block the electron tranport sytem??
 
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Via the link above:

A concentration of 1 mM KCN is sufficient to inhibit oxygen consumption by mitochondria from a vertebrate source by >98%.

Well there you go. The driving force force for the electron transport chain in the mitochondria is the presence of oxygen at the end of the chain to accept the hydrogens/electrons. No oxygen, and the whole Krebs cycle shuts down (it is the same as if you are suffocating in that respect).

This can (and probably has been) tested by seeing if CN will still have the same effect on bacteria that can ferment (respiration without the need for oxygen) and that might indirectly affirm this, but I don't have any first hand knowledge of this sort of thing.
 
That reference mentions that it inhibits oxygen consumption and has something to do with cytochrome oxidase. I remember from biochem, that carbon monoxide has a stronger affinity to hemoglobin versus oxygen and competitively inhibits oxygen uptake.. I wonder how CN inhibits oxygen uptake? (time to go dig out my biochem book):smile:
 
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This website offers a somewhat clearer statement of the mechanism involved, and even a treatment of sorts:

http://www.manbir-online.com/diseases/cyanide.htm

It seems like this is a similar idea to Carbon Monoxide poisioning (where it binds and inhibits the ability for Oxygen to bind), only this seems to take place with an enzyme specific to the mitochondria.
 
https://www.discovermagazine.com/the-deadliest-spider-in-the-world-ends-lives-in-hours-but-its-venom-may-inspire-medical-miracles-48107 https://en.wikipedia.org/wiki/Versutoxin#Mechanism_behind_Neurotoxic_Properties https://www.sciencedirect.com/science/article/abs/pii/S0028390817301557 (subscription or purchase requred) he structure of versutoxin (δ-atracotoxin-Hv1) provides insights into the binding of site 3 neurotoxins to the voltage-gated sodium channel...
Popular article referring to the BA.2 variant: Popular article: (many words, little data) https://www.cnn.com/2022/02/17/health/ba-2-covid-severity/index.html Preprint article referring to the BA.2 variant: Preprint article: (At 52 pages, too many words!) https://www.biorxiv.org/content/10.1101/2022.02.14.480335v1.full.pdf [edited 1hr. after posting: Added preprint Abstract] Cheers, Tom
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