Overall reaction:
6CO₂ + 6H₂O + light energy → C₆H₁₂O₆ + 6O₂
Detailed Breakdown:
1. Light-dependent reactions:
* Photolysis of water: 2H₂O → 4H⁺ + 4e⁻ + O₂
* Electron transport chain: Electrons from water are passed through a series of electron carriers, releasing energy to generate ATP and NADPH.
* Light absorption by chlorophyll: Light energy is absorbed by chlorophyll and used to energize electrons.
2. Light-independent reactions (Calvin cycle):
* Carbon fixation: CO₂ is incorporated into an organic molecule (RuBP) by the enzyme rubisco.
* Reduction: The carbon compound is reduced using NADPH and ATP to produce glucose (C₆H₁₂O₆).
* Regeneration: RuBP is regenerated to continue the cycle.
Overall reaction:
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ATP (energy)
Detailed Breakdown:
1. Glycolysis:
* Glucose is broken down into pyruvate, producing a small amount of ATP and NADH.
* This process occurs in the cytoplasm.
2. Pyruvate oxidation:
* Pyruvate is converted to acetyl-CoA, generating NADH and releasing CO₂.
* This process occurs in the mitochondrial matrix.
3. Krebs cycle (Citric acid cycle):
* Acetyl-CoA enters the cycle, generating ATP, NADH, FADH₂, and releasing CO₂.
* This process occurs in the mitochondrial matrix.
4. Electron transport chain:
* Electrons from NADH and FADH₂ are passed through a series of electron carriers, releasing energy to generate ATP.
* This process occurs in the inner mitochondrial membrane.
Key differences:
* Photosynthesis uses light energy to create glucose and oxygen, while cellular respiration uses glucose and oxygen to generate energy (ATP).
* Photosynthesis takes place in chloroplasts, while cellular respiration occurs in the cytoplasm and mitochondria.
* Photosynthesis is an anabolic process (building complex molecules), while cellular respiration is catabolic (breaking down complex molecules).
These two processes are interconnected and essential for life on Earth. Photosynthesis produces the food and oxygen that organisms need to survive, while cellular respiration breaks down that food to generate energy.
