Splitting of water molecules
In Photosystem II, electrons excited by sunlight are replaced by electrons derived from the splitting of water molecules (photolysis). This process releases oxygen as a byproduct and provides the necessary electrons to replenish those lost by the chlorophyll when it absorbs light energy. In Photosystem I, the excited electrons are eventually transferred to NADP+, forming NADPH, which is crucial for the Calvin cycle in photosynthesis.
During non-cyclic electron flow, electrons come from water molecules that are split by photosystem II. These electrons replace the ones lost by photosystem II as they are passed along the electron transport chain.
In photosystem II (PSII), electrons are replaced by molecules of water (H₂O). When light energy is absorbed by chlorophyll, it energizes electrons, which are then transferred to the electron transport chain. The splitting of water molecules, a process known as photolysis, occurs to replenish these lost electrons, producing oxygen gas (O₂) as a byproduct. This reaction is crucial for maintaining the flow of electrons necessary for photosynthesis.
Water participates directly in the light reactions of photosynthesis by donating electrons to photosystem II during the process of photolysis. These electrons are used to replace the ones lost by chlorophyll when it absorbs light energy, allowing the photosystem to continue absorbing light and generating ATP and NADPH for the Calvin cycle.
Photosystem II (PSII) obtains its replacement electrons from water molecules during the process of photolysis. When water is split into oxygen, protons, and electrons, the electrons released are used to replenish those lost by PSII after it absorbs light energy. This process also generates oxygen as a byproduct, which is released into the atmosphere.
During non-cyclic electron flow, electrons come from water molecules that are split by photosystem II. These electrons replace the ones lost by photosystem II as they are passed along the electron transport chain.
From energy in photons
Water participates directly in the light reactions of photosynthesis by donating electrons to photosystem II during the process of photolysis. These electrons are used to replace the ones lost by chlorophyll when it absorbs light energy, allowing the photosystem to continue absorbing light and generating ATP and NADPH for the Calvin cycle.
The supply of electrons in photosynthesis comes from water molecules. This process, known as photolysis, occurs in the light-dependent reactions of photosynthesis. Water molecules are broken down into oxygen, protons, and electrons, with the electrons being used to replenish the electrons lost in the photosystem II reaction center.
Electrons for photosystem II come from the splitting of water molecules during the light-dependent reactions of photosynthesis. This process, known as photolysis, occurs in the thylakoid membranes of chloroplasts. The electrons released from water molecules replace those lost by chlorophyll molecules in photosystem II, allowing the photosystem to continue the electron transport chain and ultimately produce ATP and NADPH for the Calvin cycle.
The thylakoid membrane contains 2 photosytems, known as Photosystem I and Photosystem II. Together, they function to absorb light and transfer energy to electrons.
Photosystem II (PSII) plays a crucial role in the light reactions of photosynthesis by capturing light energy and using it to energize electrons. This process initiates the photolysis of water, splitting it into oxygen, protons, and electrons. The energized electrons from PSII are then transferred to the electron transport chain, ultimately contributing to the synthesis of ATP and NADPH, which are essential for the Calvin cycle. Additionally, PSII helps to replenish its lost electrons by extracting them from water molecules.
Photosystem I absorbs light best at a wavelength of 700 nm, while Photosystem II absorbs light best at a wavelength of 680 nm. Photosystem I transfers electrons to reduce NADP+ to NADPH, while Photosystem II replenishes electrons lost in the process of photosynthesis. Both photosystems work together in the light-dependent reactions of photosynthesis to ultimately produce ATP and NADPH.
In photosynthesis, electrons flow from water molecules to photosystem II, then to photosystem I, and finally to NADP+ ultimately producing NADPH. Along the way, the electrons generate a proton gradient that drives ATP production.
Oxidized P680 receives its electrons, from water oxidization. (2H2O --> O2 + 4H+ + 4e-).
They go into photosystem I.
Photosystem II most likely evolved first because it provides the energy for producing ATP and passes its electrons to photosystem I.