WAEC Biology 2025 Papers

Concept:Aerobic respiration of one glucose molecule requires 6 oxygen molecules. Multiply by the number of glucose molecules.Explanation:The balanced equation for aerobic respiration is: $$\mathrm{C}_6\mathrm{H}_{12}\mathrm{O}_6 + 6\mathrm{O}_2 \rightarrow 6\mathrm{CO}_2 + 6\mathrm{H}_2\mathrm{O}$$ This equation shows that 1 molecule of glucose uses 6 molecules of oxygen. For 3 molecules of glucose, the oxygen requirement becomes: $$3 \times 6 = 18$$ Thus, 18 molecules of oxygen are needed to respire 3 glucose molecules aerobically.Answer:The correct option is D. 18 molecules of oxygen.