How are photosynthesis and cellular respiration related?

• A. Photosynthesis stores energy as glucose; cellular respiration breaks glucose down to ATP
• B. Photosynthesis consumes ATP to make glucose
• C. Cellular respiration creates glucose which photosynthesis uses to produce ATP
• D. Both processes require oxygen to produce energy in equal amounts

Answer: (A)

The main idea is energy flow between these two processes. Photosynthesis captures light energy to build glucose, storing energy in chemical bonds. Cellular respiration then breaks that glucose down to release energy and make ATP, the cell’s usable energy. So, glucose acts as the energy carrier: energy from sunlight is stored in glucose during photosynthesis, and that stored energy is released as ATP during cellular respiration.

That’s why the best answer says photosynthesis stores energy as glucose and cellular respiration breaks glucose down to ATP. The other options mix up the direction or requirements: photosynthesis isn’t simply using ATP to make glucose, respiration doesn’t create glucose, and both processes don’t require oxygen in the same way or produce energy in equal amounts.