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Water. Photosystem II uses light energy to catalyze the following reaction:
2 H2O --> 4H+ + 4e- + O2
The electrons from water pass through photosystem II to reduce quinone molecules, which shuttle the electrons to the next step of the photosynthetic reaction chain.
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∙ 14y ago
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Where do the electron get their energy in photosystem 1?
They pass through a series of compounds to photosystem I, losing energy along the way. Photosystem I, like photosystem II, emits high-energy electrons in the light, and the electrons from photosystem II replace these. Photosystem II contains chlorophyll molecules. When a photon (quantum of light) reaches one of these chlorophyll molecules, the light energy activates an electron. This is then passed to the reaction center of the photosystem, where there are two molecules of chlorophyll P680. These pass the electrons to plastoquinone, which, like the chlorophylls, is embedded in the thylakoid membrane. The plastoquinone changes its position within the membrane, and passes the electrons to cytochromes b6 and f. At this stage the electrons part with a significant proportion of their energy, which is used to pump protons (H+) into the thylakoid lumen. These protons will later be used to generate ATP by chemiosmosis. The electrons now pass to plastocyanin, which is outside the membrane on the lumen side. Photosystem I is affected by light in much the same way as photosystem II. Chlorophyll P700 passes an activated electron to ferredoxin, which is in the stroma (the liquid outside the thylakoid). Ferredoxin in turn passes the electrons on, reducing NADP+ to NADPH + H+. Photosystem I accepts electrons from plastocyanin. So, effectively, photosystem II donates electrons to photosystem I, to replace those lost from photosystem I in sunlight. How does photosystem II recover electrons? When it loses an electron, photosystem II becomes an oxidizing agent, and splits water: 2H2O forms 4H+ + 4e- + O2. The electrons return photosystem II to its original state, and the protons add to the H+ concentration in the thylakoid lumen, for later use in chemiosmosis. The oxygen diffuses away.
Where do electrons get their energy in photosystem I?
From energy in photons
How do electrons gain energy in photosystem I?
They absorb photons.
What is the explanation for the pathway of electron transport chain?
It's a pathway where electrons are transported from photosystem 2 to photosystem 1.
Electrons from what replaces the electrons from photosystem 2 during noncyclic electron flow?
water
How many times are electrons energized during photosynthesis?
The thylakoid membrane contains 2 photosytems, known as Photosystem I and Photosystem II. Together, they function to absorb light and transfer energy to electrons.
Where do electrons get their energy in photosystem II?
From energy in photons
Water participates directly in the light reactions of photosynthesis by?
Water participates directly in the light reactions of photosynthesis by donating electrons to photosystem II. Photosystem I and photosystem II both contain chlorophyll as molecules.
What happens to electrons when pigments in photosystem II absorbs light?
they move through an electron transport chain to photosystem 1
How does electrons move photosytem II to photosytem?
No, they move from photosystem 2 to photosystem 1. 2 evolved first but was not discovered until after photosystem 1.
How photosystem I and II replenish its lost electrons?
Splitting of water molecules
Where do electrons come from and how it gains energy during the light reaction?
They come from Photosystem ll. Photosystem ll gets them by ripping the electrons off of water by a process called photolysis. Electrons gain energy first in Photosystem ll, then later in photosystem l, through the absorption of energy from light.
Which photosystem most likely envolved first?
Photosystem II most likely evolved first because it provides the energy for producing ATP and passes its electrons to photosystem I.
After electrons leave photosystem II they go into an electron transport chain of three protein complexes Where do they go after that electron transport chain?
They go into photosystem I.
What sequence accurately reflects the flow of electrons in photosynthesis?
The flow of electrons in photosynthesis has four sequential steps. Here is the sequence: from water to photosystem II then photosystem I and lastly NADP.
How does water participates directly in the light reactions of photosynthesis?
donating electrons to photosystem II
After electrons leave photosystem II they go into an electron transport chain of three protein complexes. Where do they go after that electron transport chain?
They go into photosystem I.
