BioMasterPhotosynthesis vs cellular respiration
Two processes that look opposite and so get confused. Here you see their equations, where they occur and why they actually complement each other.
Direct answer: Photosynthesis occurs in the chloroplasts and builds glucose from CO₂, water and light, releasing O₂ (anabolic process, stores energy). Cellular respiration occurs in the mitochondria and breaks down glucose with O₂ to release energy (ATP), producing CO₂ and water (catabolic process). They are inverse, complementary processes.
Equations
Photosynthesis: 6 CO₂ + 6 H₂O + light → C₆H₁₂O₆ + 6 O₂
Cellular respiration: C₆H₁₂O₆ + 6 O₂ → 6 CO₂ + 6 H₂O + ATP
Notice that one is essentially the reverse reaction of the other.
Comparison table
| Photosynthesis | Cellular respiration | |
|---|---|---|
| Where | Chloroplast | Mitochondrion (glycolysis in cytoplasm) |
| Reactants | CO₂, H₂O, light | Glucose, O₂ |
| Products | Glucose, O₂ | CO₂, H₂O, ATP |
| Energy | Stores it (anabolic) | Releases it (catabolic) |
| Stages | Light reactions + Calvin cycle | Glycolysis + Krebs cycle + electron transport chain |
| Who does it | Photosynthetic organisms | Almost all cells |
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Study Biology free on BioMasterFrequently asked questions
What is the difference between photosynthesis and cellular respiration?
Photosynthesis builds glucose and stores energy in the chloroplast; cellular respiration breaks down glucose and releases energy (ATP) in the mitochondrion.
Are they opposite processes?
They are inverse and complementary: their equations are nearly opposite and together they form a cycle of energy and matter.
Do plants also respire?
Yes. Plants carry out both photosynthesis and cellular respiration; they respire day and night.