Photosynthesis

Photosynthesis: the synthesis of organic substances from carbon dioxide and water in the chloroplasts of green plants under the influence of light energy.

General equation: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂.

1. Sunlight and H₂O
2. Light phase (grana): chlorophyll absorbs light, water is split (photolysis)
3. O₂ is released, ATP and NADP·H are formed
4. Dark phase (stroma, Calvin cycle): CO₂ is fixed
5. Glucose is synthesized

• The light phase takes place on the thylakoid membranes (in the grana). As a result, ATP and NADP·H are formed.
• The dark phase takes place in the stroma (Calvin cycle): CO₂ is fixed and glucose is synthesized. ATP and NADP·H are consumed.

Key facts

• The oxygen that is released comes from water (photolysis), not from CO₂.
• Chlorophyll absorbs red and blue light well and reflects green light (that is why leaves are green).
• Products of photosynthesis: glucose and O₂. Photosynthesis is the source of oxygen and organic substances on Earth.
• Chemosynthesis: bacteria that obtain energy from the oxidation of inorganic substances (nitrifying bacteria, iron bacteria, sulfur bacteria).
• C₄ plants (maize, sugarcane) assimilate CO₂ more efficiently.