Final answer:
The reactants in cellular respiration, the process that releases energy in cells, are oxygen and glucose.
Step-by-step explanation:
The two substances that are reactants in the chemical process that releases energy in cells, also known as cellular respiration, are oxygen (O₂) and glucose (C₆H₁₂O₆). In this biochemical process, cells break down glucose in the presence of oxygen to release carbon dioxide, water, and energy.
The reaction can be represented by the chemical equation:
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + Energy
This process is critical for life as it provides the necessary energy for various cellular activities.