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Questions and Answers
Which organisms are capable of photosynthesis?
Which organisms are capable of photosynthesis?
What is the primary pigment involved in photosynthesis?
What is the primary pigment involved in photosynthesis?
Where does photosynthesis primarily occur in plant cells?
Where does photosynthesis primarily occur in plant cells?
What is the main product of the photosynthesis equation 6 CO2 + 6 H2O (sunlight) 🡪 C6H12O6 + 6 O2?
What is the main product of the photosynthesis equation 6 CO2 + 6 H2O (sunlight) 🡪 C6H12O6 + 6 O2?
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What is the theory that explains the origin of chloroplasts?
What is the theory that explains the origin of chloroplasts?
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What stage of photosynthesis occurs in the thylakoid membranes?
What stage of photosynthesis occurs in the thylakoid membranes?
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Which wavelengths of light do chlorophylls a and b primarily absorb?
Which wavelengths of light do chlorophylls a and b primarily absorb?
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What is the primary role of photosystems in photosynthesis?
What is the primary role of photosystems in photosynthesis?
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Study Notes
Photosynthesis
- Photosynthesis sustains life on Earth
- Photosynthetic organisms include plants, algae, cyanobacteria, and some protists
- These organisms transform sunlight's radiant energy into chemical energy
- Key pigment is chlorophyll, plus other pigments
- The process of photosynthesis occurs within chloroplasts
- The reaction is: 6 CO₂ + 6 H₂O (sunlight) → C₆H₁₂O₆ + 6O₂ (Carbon Dioxide + Water → Glucose + Oxygen)
Chloroplast
- Chloroplasts likely evolved from free-living photosynthetic prokaryotic cells
- This is the endosymbiotic theory
- Chloroplasts have a double membrane, inner membrane with ETC proteins
- Chloroplasts also have ribosomes, circular DNA for independent reproduction & DNA sequence similar to bacteria
Chloroplasts & Photosynthesis
- Photosynthesis in palisade cells has two stages
- Light reaction occurs in thylakoids (light energy captured by pigments, electrons released, water broken down releasing electrons and oxygen)
- Dark reaction occurs in stroma (NADPH, CO₂, ATP energy used to make glucose)
Electromagnetic Spectrum
- Sunlight is a mixture of photons with different energies
- A spectroscope separates light into different energies, creating the electromagnetic spectrum
- Most photons are invisible, but a band from about 380nm (violet) to 750nm (red) is visible light
Photosystems
- Photosystems are clusters of photosynthetic pigments embedded in thylakoid membranes
- Pigments are chemical substances produced by plants that absorb specific wavelengths of light
Plant Pigments
- Plant pigments are categorized into photosynthetic and protective pigments
- Photosynthetic pigments include chlorophylls (green), carotenoids (yellow/orange), and xanthophylls (yellow)
- Protective pigments include anthocyanins (red/purple/blue)
Absorption Spectrum
- Chlorophylls a and b absorb blue-violet and red light, reflecting green light, making plants appear green
- Other pigments absorb different wavelengths than chlorophyll, together they cover a broad range of the visible spectrum
Photosynthesis: Light Reaction
- In the thylakoid membrane, light energy is captured by pigments, which release electrons
- Water is broken down, releasing electrons and producing oxygen as a waste product
- Free electrons travel through membrane proteins (ETC), producing ATP and NADPH, which move to the dark reaction
Photosynthesis: Dark Reaction (Calvin Cycle)
- In the stroma, NADPH, CO₂, and ATP energy are used to make glucose
- The Calvin cycle includes carbon fixation, regeneration of CO₂ acceptor, and reduction
Uses of Products
- Glucose can be used in cellular respiration in the same palisade cell
- Glucose can be combined to form sucrose (transports sugars in phloem)
- Glucose can be joined into starch for storage
- Oxygen is released as a waste product, used in cellular respiration in the same palisade cell
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Description
Explore the fascinating process of photosynthesis and the role of chloroplasts in converting sunlight into chemical energy. This quiz covers the mechanisms, pigment involvement, and the evolutionary background of chloroplasts. Test your knowledge about these essential biological processes.
