Question

why do many prokaryotic and eukaryotic cells need oxygen?

Answer 1

Cellular respiration occurs in both eukaryotic and prokaryotic cells. This is an efficient way for cells to harvest energy stored in food. It has three main stages: glycolysis, the citric acid cycle, and electron transport. All these cycles requires oxygen directly or indirectly

In the presence of oxygen, glycolysis is the first stage of cellular respiration.The Citric Acid Cycle occurs only when oxygen is present but it doesn't use oxygen directly. Electron Transport requires oxygen directly.