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Questions and Answers
Where is the site of the light dependent reaction?
Where is the site of the light dependent reaction?
The thylakoids of chloroplasts.
How are chloroplasts structurally adapted to capture sunlight?
How are chloroplasts structurally adapted to capture sunlight?
The thylakoid membranes provide a large surface area for chlorophyll, and proteins hold them for maximum light absorption.
What is the simple explanation of the light dependent reaction?
What is the simple explanation of the light dependent reaction?
Light photon hits chlorophyll, hydrolysis of H2O occurs, electrons gain energy, ATP is formed, and reduced NADP is generated.
What happens in the light dependent reaction?
What happens in the light dependent reaction?
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What happens to the products of the light dependent reaction?
What happens to the products of the light dependent reaction?
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Where is the site of the light independent reaction?
Where is the site of the light independent reaction?
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How are chloroplasts adapted to carry out the light independent reaction?
How are chloroplasts adapted to carry out the light independent reaction?
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What is the simple version of the Calvin Cycle?
What is the simple version of the Calvin Cycle?
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What happens in the light independent reaction?
What happens in the light independent reaction?
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Why does the Calvin cycle turn six times to make one hexose sugar?
Why does the Calvin cycle turn six times to make one hexose sugar?
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Describe what happens during the light-dependent reaction.
Describe what happens during the light-dependent reaction.
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Study Notes
Light Dependent Reactions
- Occur in thylakoids of chloroplasts, which are stacked structures called grana.
- Thylakoid membranes have a large surface area for chlorophyll and enzymes, optimizing light absorption.
- Protein networks in grana help position chlorophyll for maximum light capture.
- ATP is synthesized on grana membranes, containing enzymes for this process.
- Chloroplasts have their own DNA and ribosomes for efficient protein production.
Process of Light Dependent Reactions
- Light photons excite electrons in chlorophyll, initiating the reaction.
- Water molecules undergo photolysis, producing electrons, protons, and oxygen.
- Excited electrons travel through the electron transport chain, generating ATP by joining ADP with inorganic phosphate (Pi).
- Reduced NADP is formed by transferring excited electrons and protons from chlorophyll.
Products of Light Dependent Reactions
- NADPH, a high-energy electron carrier, is essential for light independent reactions.
- Oxygen produced from photolysis is released as a byproduct, used in respiration or diffused out of the leaf.
Light Independent Reactions (Calvin Cycle)
- Take place in the stroma of chloroplasts.
- Stroma contains enzymes necessary for fixing CO2 and manufacturing glucose.
- Fluid around grana allows easy diffusion of products from light dependent reactions.
- Chloroplasts have their own DNA and ribosomes for rapid protein synthesis needed in this stage.
Calvin Cycle Overview
- Begins with ribulose bisphosphate (RuBP), a 5-carbon compound that captures CO2.
- The enzyme-driven reaction produces two molecules of glycerate 3-phosphate (GP).
- ATP and NADPH from the light dependent reactions convert GP to triose phosphate.
- Some triose phosphates become glucose, while others regenerate RuBP.
Cycle Requirements
- To form one hexose sugar (C6H12O6), the Calvin Cycle must turn six times to produce sufficient triose phosphates.
- Each set of three turns yields six triose phosphates, yielding two usable for glucose while others regenerate RuBP.
- Six turns necessitate 18 ATP and 12 reduced NADP from light dependent reactions.
Summarized Events of Light Dependent Reactions
- Chlorophyll absorbs light energy, exciting electrons.
- Excited electrons move through an electron transport chain, releasing energy for ATP formation.
- Water photolysis results in the release of protons, electrons, and oxygen.
- NADP is reduced by accepting hydrogen and excited electrons, preparing for the light independent phase.
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Test your knowledge on the light dependent and independent reactions of photosynthesis with these flashcard prompts. Delve into the intricate details of chloroplast structure and functionality as they relate to sunlight capture and energy transformation.
