A. to help readers understand the process of photosynthesis B. to help readers visualize the interdependency of two processes
C. to help readers visualize how glucose is stored as food
D. to help readers understand how chemical pathways function

Photosynthesis and Cellular Respiration

The processes of photosynthesis and cellular respiration are interdependent—each process is necessary to fuel the other. The chemical products of photosynthesis are the chemical reactants of cellular respiration, and the products of cellular respiration are the reactants of photosynthesis.

During photosynthesis, plants, algae, and photosynthetic bacteria—together called producers—create their own food by capturing light energy from the Sun to make molecules of glucose. Organic molecules, including glucose, can then be stored as food to be broken down by cellular respiration when energy is needed.
All living organisms perform some kind of cellular respiration. During cellular respiration, chemical pathways containing organic molecules such as glucose are broken down to release energy in a quickly usable form. Essentially, cellular respiration is the opposite of photosynthesis.