Q. 92 When cells are treated with cyanide, which ONE of the following organelles will have the highest
level of cyanide inside?
(A) Mitochondria
(B) Peroxisomes
(C) Lysosomes
(D) Endoplasmic reticulum
Cyanide primarily targets mitochondria due to its binding to cytochrome c oxidase in the electron transport chain. When cells are treated with cyanide, the highest levels accumulate in mitochondria, making option (A) correct. This disrupts ATP production and leads to rapid accumulation there.
Correct Answer
Mitochondria (A) will have the highest level of cyanide inside when cells are treated.
Cyanide acts as a potent inhibitor of cytochrome c oxidase (Complex IV) in the mitochondrial electron transport chain, binding tightly to its heme a3 group. This halts oxidative phosphorylation, the main ATP production pathway, causing cyanide to concentrate in mitochondria as it gets trapped during respiration. Cells rely on mitochondria for aerobic energy, so exposure leads to preferential accumulation there over other organelles.
Option Breakdown
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Mitochondria (A): Correct, as cyanide specifically binds respiratory chain proteins, leading to highest accumulation.
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Peroxisomes (B): Incorrect; peroxisomes handle fatty acid oxidation and ROS detoxification but lack cyanide-binding targets like Complex IV.
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Lysosomes (C): Incorrect; lysosomes degrade macromolecules via hydrolytic enzymes and do not participate in cyanide-sensitive ATP synthesis.
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Endoplasmic Reticulum (D): Incorrect; ER manages protein folding and lipid synthesis without involvement in cyanide-targeted respiration.
This MCQ tests knowledge of organelle functions in cellular respiration, vital for biology students and researchers in biochemistry or cell biology.
