Photosynthesis

Photosynthesis

• Photo – light
• Synthesis – make
• “make with light”
• Energy from the sun is transformed into chemical energy.
• Plants need sunlight so that they have the energy to change water and carbon dioxide into food (glucose) and oxygen.

Water + Carbon Dioxide + Sunlight 🡪 Glucose + Oxygen

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H₂O + CO₂  + Light Energy 🡪 C₆H₁₂O₆  + O₂

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6H₂O + 6CO₂  + Light Energy 🡪 C₆H₁₂O₆  + 6O₂  

stuff plants need (reactants)

stuff plants make (products)

Two Main Steps

• Light Dependent (light is needed)

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• Light Independent (light is not needed)

Light Reactions

• Takes place in the thylakoids.
• Water is split into (H H O).
• This releases energy needed for the dark reactions.
• Oxygen is released from the plant.
• The H’s are used to make starting ingredients for the dark reactions.

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Dark Reactions

• Also called Calvin Cycle or light independent reactions.
• Takes place in the stoma.
• Carbon Dioxide is combined with H’s and made into glucose.

Photosynthesis happens in all plants, protists, and cyanobacteria.

All photosynthetic organisms are green!

• To absorb energy to do photosynthesis, they have to have chlorophyll.
• Chlorophyll absorbs blue light and red light well, but mostly reflects green light, which accounts for the green color.

Questions

• Why is chlorophyll important to photosynthesis?
• Where does photosynthesis occur?
• Wait! What kind of cells are bacteria?
• What do prokaryotes NOT have?
• So, bacteria that do photosynthesis just do it in their cytoplasm.

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