Which gas present in air is essential for aerobic respiration? What is the role of this gas duringrespiration?

The gas present in air that is essential for aerobic respiration is Oxygen.

During aerobic respiration, oxygen is used as a reactant. The process occurs in three stages: glycolysis, the Krebs cycle, and the electron transport chain.

In the first stage, glucose is broken down in the cytoplasm of cells during a process called glycolysis, producing a small amount of energy and a molecule called pyruvate.

In the second stage, the pyruvate is transported into the mitochondria, where it is further broken down in the Krebs cycle (also known as the citric acid cycle). This process releases carbon dioxide as a waste product and transfers high-energy electrons to carrier molecules.

In the third and final stage, these high-energy electrons are used in the electron transport chain to pump hydrogen ions across the inner mitochondrial membrane. This creates a concentration gradient that drives the synthesis of a large amount of ATP (the molecule that provides energy for cellular processes) when the ions flow back across the membrane. Oxygen is the final electron acceptor in this process, combining with electrons and hydrogen ions to form water.

Without oxygen, the electron transport chain cannot occur, and the majority of the ATP produced during respiration would not be made. This is why oxygen is essential for aerobic respiration.