Question

A deep sea bacterium produces the mineral magnetite. When cyanide (a chemical that disrupts the electron transport chain) is added, no more magnetite is produced. Does this support or undermine the hypothesis that this bacterium is capable of respiration? Explain your reasoning.

Answer 1

Ans: As given in the question that bacterium produces the mineral magnetite which has the formula of Fe₃O₄ and in Fe₃O₄, 2 Fe ions has +3 oxidation state and one Fe ion has +2 oxidation state. Now electron transport chain is consists of four complex through which highe energy electrons are passed and utilized for the generation of ATP production.

Now cyanide binds to the cytochrome C oxidase which is complex IV and disrupts its function and also the electron transport chain.

Now this cytochrome IV complex receives electrons from complex III in which the iron ion at its core is reduced and oxidized as it passes the electrons, fluctuating between different oxidation states: Fe⁺⁺ (reduced) and Fe⁺⁺⁺ (oxidized).

Now because of the disruption of complex IV by the cyanide, the reduced Fe ions cannot pass the electrons to the complex IV and hence the reduced iron ion will not change into oxidized form (Fe⁺³) and hence no magnetite will be produced by the bacteria as Fe⁺³ ions are not produced in electron transport chain because of the function of cyanide.

Hence from all this we can say that the addition of cyanide and no more production of magnetite is supporting the hypothesis that this bacterium is capable of respiration.