The primary role of O2 in cellular respiration is to:Act as an acceptor of electrons and protons forming waterCombine with carbon forming CO2Catalyse reactions of glycolysisCombine with lactate, forming pyruvate

The primary role of O2 (oxygen) in cellular respiration is to act as an acceptor of electrons and protons, forming water.

Here's a step-by-step explanation:

1. Cellular respiration is a set of metabolic reactions that take place in cells to convert biochemical energy from nutrients into adenosine triphosphate (ATP), and then release waste products.

2. The reactions involved in respiration are catabolic reactions, which break down large molecules into smaller ones, releasing energy in the process.

3. Oxygen is the final electron acceptor in the electron transport chain, a part of the process of cellular respiration.

4. In the electron transport chain, electrons are passed along a series of proteins and other molecules. Each time an electron is transferred, it releases energy.

5. The final step of this process involves oxygen. The oxygen molecule accepts electrons and protons (H+ ions) to form water.

6. This reaction is crucial because it removes electrons from the system, allowing the electron transport chain to continue functioning. If oxygen were not present to accept the electrons, the chain would become backed up and cease to operate, halting the production of ATP.

So, the primary role of oxygen in cellular respiration is to act as an acceptor of electrons and protons, forming water.