Energy used to power photosynthesis & ultimately cellular respiration originates from which energy source?

• A. Glucose.
• B. ATP.
• C. Carbon dioxide.
• D. The sun.

Answer: (D)

Verified step by step guidance

1. Understand that photosynthesis is the process by which plants, algae, and some bacteria convert light energy into chemical energy stored in glucose.
2. Recognize that the energy used in photosynthesis comes from sunlight, which is absorbed by chlorophyll in the chloroplasts of plant cells.
3. Identify that the light energy from the sun is converted into chemical energy in the form of ATP and NADPH during the light-dependent reactions of photosynthesis.
4. Acknowledge that the chemical energy stored in ATP and NADPH is then used in the Calvin cycle to convert carbon dioxide and water into glucose.
5. Conclude that the ultimate source of energy for both photosynthesis and cellular respiration is the sun, as it initiates the process of energy conversion in plants.