Which gas is essential for human respiration?

Oxygen is essential for human respiration because it is the primary gas that the body requires to produce energy at the cellular level through a process called cellular respiration. In this process, oxygen is utilized in the mitochondria of cells to convert glucose and other substrates into adenosine triphosphate (ATP), which is the energy currency of the cell. This energy is crucial for various bodily functions, including muscle contraction, nerve transmission, and maintaining cellular integrity.

During respiration, the body inhales oxygen from the atmosphere, which is then transported through the bloodstream to cells. Without sufficient oxygen, cells cannot perform their necessary functions, leading to fatigue, difficulty in maintaining bodily processes, and ultimately, harm to the organism.

While carbon dioxide is a product of respiration and is necessary for maintaining the acid-base balance in the body, it is not essential for initiating the process of respiration itself. Nitrogen, which makes up a large portion of the atmosphere, is largely inert and does not play a direct role in human respiration. Hydrogen, although an important element in many biological compounds, is not a gas that is used in the respiration process as required by humans. Thus, oxygen stands out as the critical gas for supporting life through respiration.