Step 3: Compare the other options. The second equation, $\mathrm{C_6H_{12}O_6} \rightarrow 2\,\mathrm{C_2H_5OH} + 2\,\mathrm{CO_2}$, represents fermentation, not cellular respiration. The third equation, $6\,\mathrm{CO_2} + 6\,\mathrm{H_2O} \rightarrow \mathrm{C_6H_{12}O_6} + 6\,\mathrm{O_2}$, describes photosynthesis, which is the reverse of cellular respiration. The fourth equation, $2\,\mathrm{H_2O} + 2\,\mathrm{CO_2} \rightarrow \mathrm{C_2H_4O_2} + 2\,\mathrm{O_2}$, does not represent a biological process related to cellular respiration.