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Photosynthesis and Related Concepts in General Biology

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  • What are photoautotrophs?

    Photoautotrophs are organisms like plants, algae, and some protists and bacteria that produce their own food using light energy through photosynthesis.

  • What is the role of chlorophyll in photosynthesis?

    Chlorophyll is a light-absorbing pigment in chloroplasts that converts solar energy into chemical energy during photosynthesis.

  • Where does photosynthesis occur in plant cells?

    Photosynthesis occurs in chloroplasts, which have a double membrane, stacks of thylakoids, and a fluid called stroma.

  • What did isotope experiments reveal about the source of oxygen produced in photosynthesis?

    Oxygen produced in photosynthesis comes from water (H2O), not carbon dioxide (CO2), as shown by experiments using oxygen isotope O-18.

  • What type of chemical process is photosynthesis?

    Photosynthesis is a redox process where water is oxidized and carbon dioxide is reduced to form glucose.

  • What are the two main stages of photosynthesis?

    The two stages are the light reactions (in thylakoids) producing ATP and NADPH, and the Calvin cycle (in stroma) that fixes CO2 into sugars.

  • What is carbon fixation in photosynthesis?

    Carbon fixation is the process in the Calvin cycle where CO2 is incorporated into organic molecules.

  • What wavelengths of light drive photosynthesis most effectively?

    Chlorophyll absorbs mainly blue and red light, while green light is least effective for photosynthesis.

  • What is the function of carotenoids in photosynthesis?

    Carotenoids protect chlorophyll from damage by excessive light through photoprotection.

  • What are photosystems in the thylakoid membrane?

    Photosystems are complexes of light-harvesting pigments and proteins that capture solar energy and transfer electrons.

  • Why are two photosystems needed in the light reactions?

    Two photosystems work together to transfer electrons from water to NADP+, requiring two photons to drive the electron transport chain and produce ATP and NADPH.

  • How is ATP synthesized during the light reactions?

    ATP is made by photophosphorylation, where an electron transport chain pumps H+ into the thylakoid space, and H+ flows back through ATP synthase.

  • What are the main steps of the Calvin cycle?

    The Calvin cycle includes carbon fixation, reduction, release of G3P, and regeneration of RuBP.

  • What molecules power the Calvin cycle?

    The Calvin cycle uses ATP for energy and NADPH for electrons to reduce CO2 into sugar molecules.

  • How do C3, C4, and CAM plants differ in carbon fixation?

    They use different mechanisms to capture and use CO2 efficiently under various environmental conditions to reduce photorespiration.

  • What percentage of carbohydrates made by photosynthesis do plant mitochondria use in cellular respiration?

    About 50% of carbohydrates produced by photosynthesis are used by plant mitochondria for cellular respiration.

  • How are sugars from photosynthesis used besides energy?

    Sugars serve as starting materials for making proteins, lipids, and cellulose, which forms plant cell walls.

  • What is the greenhouse effect?

    The greenhouse effect is the warming of Earth’s atmosphere caused by gases like CO2 trapping heat.

  • How can reducing fossil fuel use and deforestation affect climate change?

    Reducing fossil fuel use and deforestation can lower greenhouse gas emissions, helping to moderate global warming and climate change.

  • Why is photosynthesis considered the most important process for life on Earth?

    Photosynthesis provides food and oxygen, supporting almost all living organisms and maintaining Earth's ecosystems.