Ontario Grade 9 Science Practice Exam 2025 – Complete Study Resource

The equation for cellular respiration is represented as C6H12O6 + 6O2 ---> 6CO2 + 6H2O. This equation shows how glucose (C6H12O6), which is a simple sugar and an important source of energy for cells, reacts with oxygen (O2) to produce carbon dioxide (CO2) and water (H2O).

During cellular respiration, organisms convert the chemical energy stored in glucose into a form that cells can use, primarily in the form of adenosine triphosphate (ATP). The process occurs in several stages, primarily in the mitochondria of cells, and is essential for obtaining energy from food.

The correct equation illustrates the fundamental process whereby nutrients (like glucose) and oxygen are transformed into waste products while releasing energy. In contrast, the other options do not represent this energy-releasing process correctly. For example, the equation that reverses the roles of products and reactants implies photosynthesis rather than respiration, where carbon dioxide and water are used to produce glucose and oxygen instead. Recognizing this difference is crucial for understanding cellular respiration and its role in the life of living organisms.