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Questions and Answers
What is the role of photosystems in the light dependent reactions of photosynthesis?
What is the role of photosystems in the light dependent reactions of photosynthesis?
- They are responsible for producing glucose.
- They release oxygen into the air.
- They contain pigments that capture light energy. (correct)
- They absorb carbon dioxide from the atmosphere.
Which wavelength corresponds to the absorption maximum of Photosystem II?
Which wavelength corresponds to the absorption maximum of Photosystem II?
- 700 nm
- 400 nm
- 680 – 690 nm (correct)
- 500 nm
What happens to Photosystem II during the light dependent reactions?
What happens to Photosystem II during the light dependent reactions?
- It produces ATP through photophosphorylation.
- It combines with Photosystem I to enhance absorption.
- It loses electrons due to photolysis of water. (correct)
- It absorbs light energy and reflects green light.
Which molecules are primarily found in the reaction center of a photosystem?
Which molecules are primarily found in the reaction center of a photosystem?
What process occurs as electrons pass through the electron carriers from PSII to PSI?
What process occurs as electrons pass through the electron carriers from PSII to PSI?
Flashcards
Antenna Complex
Antenna Complex
A collection of pigment molecules that absorb light energy and transfer it to the reaction center.
Reaction Center
Reaction Center
Two specialized chlorophyll a molecules within a photosystem that absorb light energy and release high-energy electrons.
Photosystem II (PSII)
Photosystem II (PSII)
The first stage of the light-dependent reactions, absorbing light energy with a peak at 680-690nm and releasing electrons.
Photosystem I (PSI)
Photosystem I (PSI)
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Photolysis of Water
Photolysis of Water
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Study Notes
Light Dependent Reactions (Hill Reactions)
- Photosynthesis' light-dependent reactions rely on pigments absorbing light energy.
- Pigments are organized into photosystems (two types) within the thylakoid membrane.
- Photosystems comprise:
- An antenna/light-harvesting complex, collecting light energy.
- A reaction center, containing special chlorophyll a molecules. These chlorophyll a molecules release highly energized electrons for further reactions.
- Photosystem II (P680/P690):
- Discovered second, but functions first in the light-dependent reactions.
- Absorbs light maximally at 680-690nm wavelengths.
- Photosystem I (P700):
- Discovered first.
- Absorbs light maximally at 700nm wavelengths.
- Light energy excites electrons in both photosystems (from chlorophyll a in the reaction center).
- Excited electrons are transferred to electron carriers within the thylakoid membrane.
- Electrons passing from one carrier to another lose energy. This energy powers proton pumps.
- Photosystems are oxidized (lose electrons), then reduced (gain electrons).
- PSII gains electrons from water splitting (photolysis).
- PSI gains electrons from PSII (via electron carriers).
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