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Photosynthesis and Carbon Fixation in General Biology

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Termini in questo insieme (21)

  • What is photosynthesis?

    Photosynthesis is a biological process that converts solar energy into chemical energy, using sunlight, CO2, and water to produce oxygen and carbohydrates.

  • What are the two main stages of photosynthesis?

    Photosynthesis consists of light-capturing reactions and the Calvin cycle.

  • Where do light-capturing reactions occur in chloroplasts?

    Light-capturing reactions occur in the thylakoid membranes of chloroplasts.

  • What is the role of the Calvin cycle?

    The Calvin cycle uses ATP and NADPH to fix carbon dioxide and synthesize carbohydrates in the stroma.

  • What are chloroplast thylakoids and grana?

    Thylakoids are flattened membranes where light reactions occur; grana are stacks of thylakoids.

  • What pigment is most common in photosynthesis and what light does it absorb?

    Chlorophyll is the most common pigment; it absorbs mainly red and blue light and reflects green.

  • What is the function of carotenoids in photosynthesis?

    Carotenoids are accessory pigments that absorb blue and green light, reflect yellow/orange/red, and protect chlorophyll from damage.

  • What happens when pigments absorb photons?

    Electrons are excited to higher energy states; energy can be transferred as heat, light (fluorescence), or used in photosynthesis.

  • What is a photosystem?

    A photosystem is a complex of pigments and proteins that captures light energy and transfers it to a reaction center.

  • What is the role of Photosystem II?

    Photosystem II captures light, excites electrons, splits water to produce O2, and passes electrons to the electron transport chain.

  • What is photophosphorylation?

    Photophosphorylation is ATP production driven by light energy via the proton gradient generated in the electron transport chain.

  • How does Photosystem I contribute to photosynthesis?

    Photosystem I absorbs light, excites electrons, and transfers them to NADP+ to form NADPH for the Calvin cycle.

  • What is the Z scheme in photosynthesis?

    The Z scheme describes linear electron flow from water through Photosystem II and I to NADP+, producing O2, ATP, and NADPH.

  • What is cyclic electron flow?

    Cyclic electron flow involves only Photosystem I, recycling electrons to produce ATP without NADPH or O2.

  • What is the function of stomata in leaves?

    Stomata are pores that regulate gas exchange, allowing CO2 in and O2 out while controlling water loss.

  • What are the three phases of the Calvin cycle?

    1. Carbon fixation, 2. Reduction, 3. Regeneration of RuBP.

  • What enzyme catalyzes carbon fixation in the Calvin cycle?

    Rubisco catalyzes CO2 fixation by reacting CO2 with RuBP to form 3-phosphoglycerate.

  • What is photorespiration?

    Photorespiration occurs when Rubisco reacts with O2 instead of CO2, consuming energy and releasing CO2, reducing photosynthetic efficiency.

  • How do C4 plants minimize photorespiration?

    C4 plants spatially separate carbon fixation and the Calvin cycle, using PEP carboxylase in mesophyll cells and Rubisco in bundle sheath cells.

  • How do CAM plants minimize photorespiration?

    CAM plants temporally separate carbon fixation and the Calvin cycle by fixing CO2 at night and using it during the day.

  • What is the key difference between oxygenic and anoxygenic photosynthesis?

    Oxygenic photosynthesis splits water to produce O2; anoxygenic photosynthesis uses other electron donors and does not produce O2.