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Questions and Answers
During photosynthesis, what role does water play specifically in the light-dependent reactions?
During photosynthesis, what role does water play specifically in the light-dependent reactions?
- It acts as a reactant that is split to provide electrons, protons, and oxygen. (correct)
- It absorbs photons from sunlight to initiate the electron transport chain.
- It directly fixes carbon dioxide into glucose.
- It transports carbon dioxide from the stomata to the chloroplast.
How does the regeneration of RuBP contribute to the continuation of the Calvin cycle?
How does the regeneration of RuBP contribute to the continuation of the Calvin cycle?
- It synthesizes glucose directly from carbon dioxide.
- It releases oxygen as a byproduct, supporting aerobic respiration.
- It fixes carbon dioxide, allowing the cycle to begin again. (correct)
- It produces ATP and NADPH, which are essential for the light-dependent reactions.
Suppose a plant is exposed to a toxin that inhibits the function of ATP synthase in the thylakoid membrane. Which of the following processes would be most directly affected?
Suppose a plant is exposed to a toxin that inhibits the function of ATP synthase in the thylakoid membrane. Which of the following processes would be most directly affected?
- Splitting of water molecules.
- Synthesis of ATP from ADP and inorganic phosphate. (correct)
- Absorption of light energy by chlorophyll.
- Formation of a proton gradient.
If stomata are blocked what is MOST likely to happen to the plant and why?
If stomata are blocked what is MOST likely to happen to the plant and why?
How do electrons that are excited by light energy in Photosystem I (PSI) contribute to the production of NADPH?
How do electrons that are excited by light energy in Photosystem I (PSI) contribute to the production of NADPH?
Xylem is a plant tissue that transports water to the leaves. If a disease damages the xylem in a plant, what is the most likely consequence for photosynthesis?
Xylem is a plant tissue that transports water to the leaves. If a disease damages the xylem in a plant, what is the most likely consequence for photosynthesis?
Why is a gradient of hydrogen ions (H+) essential for ATP production in the light-dependent reactions of photosynthesis?
Why is a gradient of hydrogen ions (H+) essential for ATP production in the light-dependent reactions of photosynthesis?
A plant is genetically modified to produce a non-functional version of the enzyme that regenerates RuBP. How would this modification most likely affect the plant's ability to conduct photosynthesis?
A plant is genetically modified to produce a non-functional version of the enzyme that regenerates RuBP. How would this modification most likely affect the plant's ability to conduct photosynthesis?
What happens to NADP+ after it accepts high-energy electrons in the final step of the electron transport chain during photosynthesis?
What happens to NADP+ after it accepts high-energy electrons in the final step of the electron transport chain during photosynthesis?
How does the electron transport chain directly contribute to ATP production during the light-dependent reactions of photosynthesis?
How does the electron transport chain directly contribute to ATP production during the light-dependent reactions of photosynthesis?
Flashcards
Photosynthesis
Photosynthesis
The process where plants convert light energy into chemical energy.
Light-dependent reactions
Light-dependent reactions
Reactions that require light to produce ATP and NADPH.
Light-independent reactions (Calvin Cycle)
Light-independent reactions (Calvin Cycle)
Reactions that use ATP and NADPH to convert CO2 into glucose.
Chlorophyll
Chlorophyll
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Stomata
Stomata
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Xylem
Xylem
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Thylakoid
Thylakoid
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Stroma
Stroma
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Water splitting
Water splitting
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ATP synthase
ATP synthase
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Study Notes
- Photosynthesis consists of light-dependent and light-independent reactions
- Plants require water, carbon dioxide, and sunlight for photosynthesis
- Chlorophyll absorbs photons from sunlight
- Carbon dioxide enters and oxygen exits through stomata, which are tiny pores
- Water is absorbed by the roots and transported to the leaves via xylem tissue
- Chloroplasts are suspended in a fluid called stroma
Thylakoid
- Thylakoids store chlorophyll, stack into grana, and contain a lumen
- Thylakoid membranes have phospholipid bilayers to maintain concentration gradients
- Light-dependent reactions occur in thylakoid membranes
Photosynthesis Processes
- Photon absorption, water splitting, electron transport, and NADH and ATP formation during photosynthesis
- Light energy is absorbed in the chloroplast during Photosynthesis II
- Electrons are excited, increasing their energy state during Photosynthesis II
- Water is split to release oxygen in Photosynthesis II
- Electrons are transferred along an electron transport chain in Photosynthesis II
- Electrons passing along the electron transport chain release energy to pump H+ ions, creating a gradient
- Electrons are re-excited in Photosystem I and reduce NADP+ to NADPH
- H+ ions create a gradient, driving ATP synthase to form ATP from ADP in the final stage of light-dependent reactions
Light Dependent Reactions
- Light dependent reactions take place in the thylakoid
- The Calvin cycle is another name for light-independent reactions
- Carbon dioxide is converted into 3-PGA (carbon compounds) during the Calvin cycle
- The main purpose of light reactions is to produce glucose
- ATP and NADPH provide the energy to produce glucose
- Sugar, starch, cellulose, and lipids are formed in the light dependent reactions
- Three remaining carbon molecules regenerate RuBP and produce other organic compounds
Wavelengths and UV Rays
- From most to least powerful: gamma rays, X-rays, UV rays, visible light, infrared, microwaves, radio waves
- Shorter wavelengths have higher energy; longer wavelengths have lower energy
- Wavelength distinguishes one form of electromagnetic energy from another
- Gamma rays carry the most energy
- X-rays have a shorter wavelength than UV rays
- Infrared radiation is red
- UV light is blue/indigo/violet
Other Information
- Water is oxidized into oxygen during light reactions
- Carbon dioxide is reduced into glucose during the Calvin cycle
- Water is the source of hydrogen and electrons that end up in glucose
- Oxygen is the source of oxygen atoms that end up in glucose
- NADPH is oxidized and NADP+ is reduced in the Calvin cycle
- Oxygen is produced by the thylakoid reactions
Electron Transport Chain
- Chlorophyll loses electrons
- Byproducts of water splitting include hydrogen and oxygen ions
- Energy helps move NADPH by combining 2 electrons and 1 hydrogen atom to make NADPH+
- Energy packs an inorganic phosphate onto ADP to make ATP
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