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Questions and Answers
What is the primary product of the light-dependent reactions that provides energy for the light-independent reactions?
What is the primary product of the light-dependent reactions that provides energy for the light-independent reactions?
Photosystem II occurs after Photosystem I in the sequence of light-dependent reactions.
Photosystem II occurs after Photosystem I in the sequence of light-dependent reactions.
False
What is the role of chlorophyll in the light-dependent reactions?
What is the role of chlorophyll in the light-dependent reactions?
To trap light energy and initiate electron transport.
The light-independent reactions mainly take place in the ______ of the chloroplasts.
The light-independent reactions mainly take place in the ______ of the chloroplasts.
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Match the following processes with their descriptions:
Match the following processes with their descriptions:
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Which molecule accepts electrons during the light-dependent reactions?
Which molecule accepts electrons during the light-dependent reactions?
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The electron transport chain in the light-dependent reactions creates a gradient to produce NADPH.
The electron transport chain in the light-dependent reactions creates a gradient to produce NADPH.
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What is the Z scheme in photosynthesis?
What is the Z scheme in photosynthesis?
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Which of the following products are generated during non-cyclic phosphorylation?
Which of the following products are generated during non-cyclic phosphorylation?
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Cyclic phosphorylation produces NADPH.
Cyclic phosphorylation produces NADPH.
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What is the initial stable product of the Calvin cycle?
What is the initial stable product of the Calvin cycle?
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What is the primary function of the electron transport chain in the light-dependent reactions?
What is the primary function of the electron transport chain in the light-dependent reactions?
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The process of capturing carbon dioxide from the atmosphere and forming carbohydrates is known as __________.
The process of capturing carbon dioxide from the atmosphere and forming carbohydrates is known as __________.
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In the light-dependent reactions of photosynthesis, chlorophyll a is primarily responsible for absorbing light energy.
In the light-dependent reactions of photosynthesis, chlorophyll a is primarily responsible for absorbing light energy.
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Match the following components related to photosynthesis with their functions:
Match the following components related to photosynthesis with their functions:
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What are the two main products generated from the light-dependent reactions of photosynthesis?
What are the two main products generated from the light-dependent reactions of photosynthesis?
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What role do H+ ions play in ATP synthesis during photophosphorylation?
What role do H+ ions play in ATP synthesis during photophosphorylation?
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The process in which carbon dioxide combines with ribulose 1,5-biphosphate (RuBP) is known as the ______.
The process in which carbon dioxide combines with ribulose 1,5-biphosphate (RuBP) is known as the ______.
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Match the photosystem with their absorption peak wavelength:
Match the photosystem with their absorption peak wavelength:
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Photosystem I is involved in both cyclic and non-cyclic phosphorylation.
Photosystem I is involved in both cyclic and non-cyclic phosphorylation.
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What does photolysis of water produce during the light-dependent reactions?
What does photolysis of water produce during the light-dependent reactions?
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Which of the following factors does NOT limit the rate of photosynthesis?
Which of the following factors does NOT limit the rate of photosynthesis?
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The rate of the light-dependent reactions of photosynthesis increases indefinitely with higher light intensity.
The rate of the light-dependent reactions of photosynthesis increases indefinitely with higher light intensity.
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What is formed from two glyceraldehyde 3-phosphate (GALP) molecules during photosynthesis?
What is formed from two glyceraldehyde 3-phosphate (GALP) molecules during photosynthesis?
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Study Notes
Photosynthesis
- Photosynthesis is the process by which plants, some bacteria, and some protists use sunlight to produce glucose from carbon dioxide and water.
- This glucose can be converted into pyruvate, which releases ATP through cellular respiration. Oxygen is also a byproduct.
- The overall process can be summarized as: carbon dioxide + water + sunlight → glucose + oxygen.
- The conversion of sunlight energy to chemical energy is facilitated by chlorophyll.
Chlorophyll Structure
- Chlorophyll is a complex molecule.
- All chlorophylls have a lipid-soluble hydrocarbon tail (C20H39-).
- They also have a flat, hydrophilic head with a magnesium ion at its center; different chlorophylls have different side groups on the head.
- The tail and head are linked by an ester bond formed between hydroxyl and carboxyl groups.
Leaves and Leaf Structure
- Plants have leaves, which are solar collectors packed with photosynthetic cells.
- Water enters through xylem vessels.
- Leaves have stomata, specialized structures that allow gases to enter and exit the leaf.
- Carbon dioxide enters and oxygen leaves through the stomata.
- Stomata are flanked by guard cells that regulate their opening and closing.
- Water loss is a potential issue for land plants.
Photosynthesis: Chloroplasts and Membranes
- The thylakoid is the structural unit of photosynthesis and is present in both prokaryotic and eukaryotic organisms.
- Prokaryotes and eukaryotes both have flattened sacs/vesicles containing photosynthetic chemicals.
- Chloroplasts in eukaryotes contain a surrounding membrane.
- Thylakoids are stacked into grana, with the spaces between grana called stroma.
- Chloroplasts have three membrane systems, creating three compartments.
Stages of Photosynthesis
- Light-Dependent Reactions (grana): Light energy is absorbed by chlorophyll, leading to excited electrons. Water molecules split(photolysis), producing oxygen, hydrogen, and electrons. ATP and NADPH are produced.
- Light-Independent Reactions (stroma): The products of the light-dependent reactions, ATP and NADPH, are used to convert carbon dioxide into carbohydrates (such as glucose through the Calvin Cycle).
The Light-Dependent Reactions
- Chlorophyll absorbs light, ionizing the chlorophyll and exciting its electrons.
- Two electrons are transferred to an electron acceptor.
- The positively charged chlorophyll ion takes electrons from a neighboring electron donor (water in this case).
- Electron transfer systems carry the electrons between photosystems across the thylakoid membrane.
- The energy from this process makes ATP.
Chemiosmosis and ATP Synthesis
- H+ ions are pumped from the stroma into the thylakoid interior by electron transport, creating an electrochemical gradient .
- This gradient drives the production of ATP.
- H+ ions diffuse from high concentration to low (stroma) through ATP synthase.
- This flow activates the enzyme, producing ATP from ADP.
Cyclic Phosphorylation
- Only Photosystem I is used, producing excited electrons which travel back to Photosystem I via electron transport chain.
- More ATP is generated, but no NADPH.
The Light-Independent Reactions (Calvin Cycle)
- Carbon dioxide from the air combines with a five-carbon sugar called RuBP, creating a six-carbon sugar.
- The six-carbon sugar quickly splits into two three-carbon molecules (PGA).
- ATP and NADPH from the light-dependent reactions are consumed to convert PGA into glyceraldehyde 3-phosphate (GALP).
- Some GALP molecules are used to make glucose.
- The rest of the GALP regenerates the five-carbon sugar (RuBP), continuing the cycle.
Factors Affecting Photosynthesis
- Light intensity, carbon dioxide concentration, and temperature are the limiting factors.
- As these factors increase, the rate of photosynthesis increases until limited by another factor.
- Optimal temperatures for enzymes result in maximum rates of photosynthesis. Enzymes may be denatured by higher temperatures.
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Description
Explore the essential processes of photosynthesis and the structure of chlorophyll in plants. Understand how sunlight is converted into chemical energy and the role of leaves in this process. This quiz delves into the mechanisms behind glucose production and the importance of chlorophyll in photosynthesis.
