Cyanide (C≡N−) blocks complex IV of the electron transport chain. Suggest a hypothesis for what happens to the ETC when complex IV stops working. Your hypothesis should explain why cyanide poisoning in humans is fatal.

Verified step by step guidance

1. Understand the role of Complex IV: Complex IV, also known as cytochrome c oxidase, is the last enzyme in the electron transport chain (ETC) of mitochondria. It facilitates the transfer of electrons from cytochrome c to oxygen, the final electron acceptor, and aids in the formation of water.
2. Recognize the effect of cyanide: Cyanide binds to the iron atom in the heme group of cytochrome c oxidase, inhibiting its function. This prevents the enzyme from transferring electrons to oxygen, effectively halting the electron transport chain.
3. Hypothesize the immediate consequences: With the blockage of Complex IV, electrons cannot be transferred to oxygen, leading to a buildup of electrons within the ETC. This causes a back-up of electrons and reduces the proton gradient across the mitochondrial membrane, which is essential for ATP synthesis.
4. Link to cellular effects: The reduction in ATP synthesis due to the halted ETC leads to decreased energy availability for vital cellular processes. Cells cannot perform functions necessary for survival, leading to cell death.
5. Explain the organism-level impact: The widespread cell death, particularly in critical organs like the brain and heart, leads to system failure and ultimately results in the fatal outcome of cyanide poisoning.

Key Concepts

Electron Transport Chain (ETC)

The Electron Transport Chain is a series of protein complexes located in the inner mitochondrial membrane that facilitate the transfer of electrons derived from nutrients. This process generates a proton gradient across the membrane, which is essential for ATP production through oxidative phosphorylation. Each complex plays a crucial role in moving electrons and protons, ultimately leading to the reduction of oxygen to water.

Complex IV (Cytochrome c oxidase)

Complex IV, also known as cytochrome c oxidase, is the final enzyme in the Electron Transport Chain. It catalyzes the transfer of electrons from cytochrome c to molecular oxygen, reducing it to water. This step is vital for maintaining the flow of electrons through the ETC and for sustaining the proton gradient necessary for ATP synthesis. Inhibition of Complex IV by cyanide halts this process, leading to cellular energy failure.

Hypoxia and Cellular Respiration

Hypoxia refers to a deficiency in the amount of oxygen reaching the tissues, which can occur when Complex IV is inhibited. Without oxygen, the Electron Transport Chain cannot function, leading to a decrease in ATP production. Cells then switch to anaerobic respiration, which is less efficient and produces lactic acid, ultimately resulting in cellular damage and death. This lack of energy and buildup of toxic byproducts explain why cyanide poisoning is fatal.