Which metabolic product is commonly produced by archaea?

• A. Methane
• B. Carbon dioxide
• C. Hydrogen sulfide
• D. Ammonia

Answer: (A)

Methanogenesis is a metabolic process distinctive to many archaea, especially in oxygen-free environments. In these anaerobic settings, certain archaea use substrates such as carbon dioxide and hydrogen (or acetate) to drive energy production, releasing methane as the primary end product. This is why methane is the metabolic product most commonly associated with archaea. While carbon dioxide can appear in methanogenic reactions and other compounds like hydrogen sulfide or ammonia show up in different metabolic contexts, none are as characteristic of archaeal metabolism as methane.