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Questions and Answers
What is the name for the process by which plants use light energy to create food?
What is the name for the process by which plants use light energy to create food?
Photosynthesis
What are the two main stages of photosynthesis?
What are the two main stages of photosynthesis?
The light reactions and the Calvin cycle
What are the products of the light reactions?
What are the products of the light reactions?
Which of the following is NOT a product of the light reactions?
Which of the following is NOT a product of the light reactions?
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The Calvin cycle occurs in the stroma of the chloroplast.
The Calvin cycle occurs in the stroma of the chloroplast.
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What is the primary electron acceptor in Photosystem II?
What is the primary electron acceptor in Photosystem II?
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What is the name of the molecule that carries electrons from Photosystem II to Photosystem I?
What is the name of the molecule that carries electrons from Photosystem II to Photosystem I?
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What is the name of the molecule that is reduced to NADPH in the light reactions?
What is the name of the molecule that is reduced to NADPH in the light reactions?
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What is the name of the enzyme that produces ATP in the light reactions?
What is the name of the enzyme that produces ATP in the light reactions?
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The cyclic electron flow pathway produces both ATP and NADPH.
The cyclic electron flow pathway produces both ATP and NADPH.
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What process is responsible for the production of oxygen during photosynthesis?
What process is responsible for the production of oxygen during photosynthesis?
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What is the main function of the light-dependent reactions of photosynthesis?
What is the main function of the light-dependent reactions of photosynthesis?
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Which of the following is NOT a true statement about photosynthesis?
Which of the following is NOT a true statement about photosynthesis?
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What is the primary role of chlorophyll in photosynthesis?
What is the primary role of chlorophyll in photosynthesis?
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What is meant by the term 'photophosphorylation'?
What is meant by the term 'photophosphorylation'?
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What is the role of NADPH in photosynthesis?
What is the role of NADPH in photosynthesis?
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The Calvin cycle can occur in the dark.
The Calvin cycle can occur in the dark.
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Why is photosynthesis considered essential for life on Earth?
Why is photosynthesis considered essential for life on Earth?
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What are the main raw materials needed for photosynthesis?
What are the main raw materials needed for photosynthesis?
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Study Notes
Learning Competency
- Describe the patterns of electron flow through light reaction events. (STEM_BIO11/12-IIa-j-4)
Specific Objectives
- Determine the essential molecules involved in the light reactions
- Describe the events and processes happening during light reactions
- Distinguish the importance of sunlight to photosynthesis
Key Concepts
Why is Photosynthesis Important?
- Photosynthesis is crucial for life on Earth; autotrophs (plants) produce their food using water, carbon dioxide, and sunlight
- Heterotrophs (humans and animals) depend on plants for their food supply
- If photosynthesis stops, there would be little food and oxygen on Earth; most life forms would disappear
- Chemosynthetic bacteria are unlikely to be affected since they utilize chemical energy
Stages of Photosynthesis
- Photosynthesis is a two-stage process: light reactions and the Calvin cycle (dark reactions)
Stage One: Light Reactions
- Light reactions use sunlight to initiate electron transfer
- The process converts NADP+ to NADPH and splits water to produce oxygen
- Adenosine triphosphate (ATP) is generated through phosphorylation
- Occurs in the thylakoids within chloroplasts
Stage Two: Calvin Cycle (Dark Reactions)
- The Calvin cycle is independent of light
- Energy from ATP, produced during the light reactions, is used to combine hydrogen from light reactions with carbon dioxide to produce glucose
- Takes place in the stroma of chloroplasts
Light Reactions Events
- Light energy is absorbed by pigment molecules in Photosystem II (PS II)
- This boosts an electron to a high-energy level in chlorophyll P680, which is then passed to a primary electron acceptor
- The lost electron is replaced by an electron from a water molecule, resulting in the release of oxygen
- Electrons move through an electron transport chain, releasing energy that is used to pump hydrogen ions into the thylakoid lumen
- This creates a hydrogen gradient, facilitating the production of ATP through chemiosmosis, using ATP synthase
- Electrons are passed to Photosystem I (PS I), where they are re-energized
- Electrons are then passed to NADP+, forming NADPH, crucial for the Calvin Cycle
Cyclic Electron Flow
- A short-circuited electron pathway in Photosystem I (PS I)
- Electrons return to the electron transport chain
- ATP is synthesized but not NADPH
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Description
This quiz focuses on the light reactions of photosynthesis, covering the essential molecules involved, the processes taking place, and the significance of sunlight. It aims to enhance understanding of how plants convert light energy into chemical energy essential for life on Earth.
