The balanced chemical equation for cellular respiration of glucose (C₆H₁₂O₆) is:
\[ 6 \text{C}6\text{H}{12}\text{O}_6 + 6 \text{O}_2 \rightarrow 6 \text{CO}_2 + 6 \text{H}_2\text{O} + \text{energy} \]
From this equation, we see that 6 oxygen molecules (O₂) are required to fully oxidize 1 glucose molecule. Therefore, for 2 glucose molecules, you would need:
\[ 6 \text{O}_2 \times 2 \text{ glucose} = 12 \text{ O}_2 \]
So, the answer is 12 O₂ molecules.