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What type of plants minimizes the cost of photorespiration by incorporating carbon dioxide into four-carbon compounds?
Photorespiration generates ATP and sugars for the plant.
False
What is the primary issue with photorespiration in plants on hot, dry days?
It drains up to 50% of the carbon fixed by the Calvin cycle.
In CAM plants, stomata open at night to incorporate carbon dioxide into __________.
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What is produced during linear electron flow in photosynthesis?
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Match the type of plant with its respective carbon fixation method:
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Chlorophyll a is the only pigment involved in photosynthesis.
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What is the primary function of accessory pigments like carotenoids?
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The Calvin cycle uses _____ and NADPH to reduce carbon dioxide to sugar.
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Match each component to its function in photosynthesis:
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What happens during cyclic electron flow?
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Photorespiration contributes positively to the efficiency of photosynthesis.
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What is the molecule produced in the Calvin cycle that signifies the net synthesis of sugar?
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Which of the following stages of photosynthesis occurs in the chloroplasts?
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The light reactions utilize water and release carbon dioxide as a byproduct.
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What is the primary role of photosynthetic pigments in plants?
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In photosynthesis, water is _____ and carbon dioxide is _____ during the redox process.
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Match the following pigments with their primary absorption wavelengths:
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What part of the chloroplast contains the thylakoids?
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Photosystems are clusters of pigments and proteins that play a crucial role in the light reactions.
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What is the process called that converts light energy into chemical energy during photosynthesis?
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The electromagnetic spectrum includes all forms of _____ energy.
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Which type of light is most effective for driving photosynthesis?
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Study Notes
Engelmann's Experiment
- Different wavelengths of light exposed to a filamentous alga led to varying rates of photosynthesis.
- The areas receiving wavelengths favorable for photosynthesis produced excess oxygen.
- The growth of aerobic bacteria around the alga was used to measure oxygen production.
Chlorophyll and Accessory Pigments
- Chlorophyll a is the primary pigment involved in photosynthesis.
- Accessory pigments, like chlorophyll b, broaden the range of light wavelengths used in photosynthesis.
- Carotenoids function as accessory pigments that absorb excessive light to protect chlorophyll from damage.
Excitation of Chlorophyll by Light
- When chlorophyll absorbs light, electrons become excited and move to a higher energy level.
- As excited electrons fall back to their ground state, photons are released, resulting in fluorescence.
- An isolated solution of chlorophyll will fluoresce when illuminated, emitting light and heat.
Reaction-Center Complexes and Light-Harvesting Complexes
- A photosystem consists of a reaction-center complex surrounded by light-harvesting complexes.
- Light-harvesting complexes contain pigment molecules bound to proteins, which transfer light energy to the reaction center.
Solar-Powered Electron Transfer
- The primary electron acceptor in the reaction center accepts excited electrons, becoming reduced.
- The initial step in the light reactions involves a transfer of an electron from a chlorophyll a molecule to the primary electron acceptor, powered by light energy.
Linear Electron Flow
- Linear electron flow is the primary pathway in photosynthesis, utilizing both photosystems.
- This process uses light energy to generate ATP and NADPH.
Cyclic Electron Flow
- Cyclic electron flow involves photosystem I only, leading to ATP production but no NADPH.
- No oxygen is released during cyclic electron flow.
- This process generates surplus ATP to meet the higher demands of the Calvin cycle.
Comparison of Chemiosmosis in Chloroplasts and Mitochondria
- Both chloroplasts and mitochondria utilize chemiosmosis to generate ATP.
- Mitochondria transform chemical energy from food into ATP, while chloroplasts convert light energy into chemical energy stored in ATP.
The Calvin Cycle
- The Calvin cycle uses ATP and NADPH to reduce carbon dioxide into sugar.
- Carbon dioxide enters the cycle and exits as glyceraldehyde 3-phosphate (G3P).
- The cycle must run three times to synthesize one G3P molecule, fixing three carbon dioxide molecules.
- The Calvin cycle has three phases: carbon fixation, reduction, and regeneration of RuBP.
Photorespiration
- Rubisco can bind oxygen instead of carbon dioxide, leading to photorespiration.
- Photorespiration consumes oxygen and organic fuel, releasing carbon dioxide without producing ATP or sugar.
- Photorespiration can reduce the efficiency of carbon fixation, especially under hot and dry conditions.
C4 Plants
- C4 plants minimize photorespiration by incorporating carbon dioxide into four-carbon compounds in mesophyll cells.
- PEP carboxylase, with its higher affinity for carbon dioxide, fixes carbon dioxide even at low concentrations.
- These four-carbon compounds are transported to bundle-sheath cells, where they release carbon dioxide for use in the Calvin cycle.
CAM Plants
- CAM plants, like succulents, utilize crassulacean acid metabolism (CAM) to fix carbon.
- CAM plants open their stomata at night, incorporating carbon dioxide into organic acids.
- Stomata close during the day, releasing carbon dioxide from organic acids for use in the Calvin cycle.
Importance of Photosynthesis
- Photosynthesis converts light energy into chemical energy stored in organic compounds.
- Sugar produced in chloroplasts provides energy and building blocks for the synthesis of other organic molecules.
- Plants store excess sugar as starch in various structures like roots, tubers, seeds, and fruits.
- Photosynthesis is responsible for the oxygen in the Earth's atmosphere.
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Description
Test your knowledge on Engelmann's experiment, chlorophyll, accessory pigments, and the excitation of chlorophyll by light. Understand the processes that govern photosynthesis, including the role of different pigments in capturing light energy. This quiz will challenge your comprehension of the scientific principles related to plant biology.
