Final answer:
Sulfide inhibits cellular respiration by combining with metals present in cytochromes, which are vital for electron transport in the respiration process. The correct option is (D).
Step-by-step explanation:
Sulfide is toxic to respiring organisms because it can combine with metals present in cytochromes that serve a critical function in respiration. Cytochromes are a group of heme proteins that are essential components of the electron transport chain in mitochondria and chloroplasts. Their primary function is to facilitate electron transfer by undergoing oxidation and reduction through the metal ion present at their core, usually iron. Sulfide can bind to the metal ion in these proteins, thereby interfering with their function and inhibiting cellular respiration.
Oxygen (O₂) utilizers need intact cytochrome pathways to complete aerobic respiration efficiently. During this process, electrons are transferred through the electron transport system (ETS), ultimately reaching cytochrome c oxidase. Toxic substances, like cyanide and carbon monoxide, and also sulfide, inhibit the function of these cytochromes, particularly cytochrome c oxidase (Complex IV), thus preventing the final transfer of electrons to oxygen, the terminal electron acceptor, and impairing oxidative phosphorylation.
In comparison, components like glycolysis enzymes, oxidases, and NADH are critical for various stages of cellular respiration but are not the direct targets of sulfide's inhibitory action. The cytochromes are uniquely vulnerable to disruption by sulfide due to their metal-binding capacities which play a pivotal role in electron transport and energy production.
The correct option for this question is D) cytochromes.