Worked example 1
Photosynthesis is frequently described as the most important energy transfer process on Earth.
(a) State the initial form of energy absorbed and the final form it is converted into during photosynthesis. (b) Write the overall balanced chemical equation for photosynthesis. (c) Explain why this energy transfer is considered fundamental to sustaining life.
Show solution outline
(a) Initial energy form: Light energy (from the sun). Final energy form: Chemical energy (stored in the chemical bonds of organic molecules like glucose).
(b) Overall balanced chemical equation: 6CO₂ + 6H₂O + Light Energy → C₆H₁₂O₆ + 6O₂
(c) Explanation of fundamental importance:
- Provides energy for food chains: The glucose produced is the primary source of chemical energy for autotrophs (producers) and forms the base of nearly all food webs. Heterotrophs (consumers) obtain this stored energy by eating plants or other animals.
- Releases oxygen: Oxygen is a crucial by-product released into the atmosphere, which is essential for aerobic respiration in most living organisms, allowing them to efficiently release energy from food.
- Carbon fixation: It removes carbon dioxide from the atmosphere and converts it into organic compounds, helping to regulate atmospheric CO₂ levels and the global carbon cycle, which has implications for climate.