Nursing Entrance Exam (NEX) Practice Exam

Which molecule cited plays a crucial role in cellular respiration?

1. Oxygen

2. Carbon

3. Nitrogen

4. Hydrogen

The correct answer is: Oxygen

Oxygen is essential in cellular respiration, which is the process by which cells convert glucose into usable energy in the form of adenosine triphosphate (ATP). During this process, oxygen acts as the final electron acceptor in the electron transport chain, a series of reactions that occur in the mitochondria of eukaryotic cells. By accepting electrons, oxygen helps to combine with hydrogen ions to form water, a byproduct of cellular respiration. This step is critical because it allows the electron transport chain to continue functioning, facilitating the production of ATP through oxidative phosphorylation. In contrast, while carbon is necessary as part of the glucose molecule, and nitrogen and hydrogen play roles in other biochemical processes, such as forming amino acids and nucleic acids, they do not play the direct, crucial role that oxygen has in enabling the complete oxidation of glucose and the generation of ATP during cellular respiration.