Photosynthesis
Section: 10. Chemistry of the Environment | Syllabus: Cambridge AS Level Physics 9702
Photosynthesis Photosynthesis The process by which green plants convert carbon dioxide and water into glucose (a sugar) and oxygen, using light energy from the Sun. Chlorophyll in plant cells absorbs the light energy needed for this reaction.
Word Equation carbon dioxide + water → glucose + oxygen Symbol Equation 6CO₂(g) + 6H₂O(l) → C₆H₁₂O₆(aq) + 6O₂(g) Requirements for Photosynthesis Carbon dioxide: Absorbed from the air through stomata in leaves Water: Absorbed from the soil through roots Light energy: Usually from sunlight Chlorophyll: Green pigment in chloroplasts that absorbs light energy Products of Photosynthesis Glucose (C₆H₁₂O₆): Used by the plant for: Respiration to release energy Conversion to starch for storage Conversion to cellulose for cell walls Making proteins (when combined with nitrates from soil) Oxygen (O₂): Released into the atmosphere through stomata, used by animals and plants for respiration Importance of Photosynthesis Produces oxygen: Maintains oxygen levels in the atmosphere for respiration Removes CO₂: Helps reduce atmospheric carbon dioxide, mitigating climate change Food production: Forms the basis of food chains by producing glucose Energy storage: Converts light energy into chemical energy stored in glucose Aspect Photosynthesis Respiration Process Makes glucose from CO₂ and H₂O Breaks down glucose to release energy Energy Requires (absorbs) light energy Releases energy Reactants CO₂ + H₂O Glucose + O₂ Products Glucose + O₂ CO₂ + H₂O Occurs in Green plants only (chloroplasts) All living organisms (mitochondria) When Only during daylight (requires light) Continuously, day and night Environmental Role Photosynthesis plays a crucial role in balancing atmospheric gases: Plants absorb CO₂ produced by respiration and combustion Plants release O₂ needed for respiration by animals and other organisms Deforestation reduces photosynthesis, contributing to rising CO₂ levels Reforestation and protecting forests help combat climate change
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