Non-Cyclic Phosphorylation of Photosynthesis

In summary, during non-cyclic phosphorylation, two electrons leave PSI and travel through an electron transport chain to reduce ferredoxin. These electrons can also be used to produce ATP if there is no NADPH+ available. ATP is produced during the first step of the electron transport chain by pumping hydrogen ions into the thylakoid, creating a proton gradient for ATP synthase to utilize. In PSI, each chlorophyll molecule loses one electron, so two electrons must cycle through the electron transport chain twice. The protons pumped into the thylakoid come from the lysis of water molecules.
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Homework Statement


Dear All,

I would like to ask you a question as the concept doesn't seem to be best explained on my book.

It is stated that during non-cyclic phosphorylation two electrons (One per molecule of Chlorophyll in the reaction center.) leave PSI, travel an electron transport chain and final reach one final protein (ferredoxin) which is reduced. (For a total of two ferredoxin molecules reduced, one per electron.), these proteins are then used to reduce NADPH+ to NADPH+H+. It is also stated that should there be no NADPH+ available the electrons will cycle the electron transport chain again to produce ATP.

Is ATP produced also the first time electrons travel the electron transport chain after leaving PhotostemI?

Is ATP produced as in the first step, with Hydrogen Ions being pumped inside the thylakoid, hence producing a proton gradient, and ATP Synthase taking advantage of this potential to recharge ATP?

Also, if I understood correctly the Cholorophyll in PSII loses two electrons twice, for a total of four electrons loss, hence giving it the ability to the split a water molecule producing some additional protons as well as stabilizing itself. Does the same happen in PSI even though each Chlorophyll loses only one electron?

Are the protons pumped into the thylakoid as a result of ETC post PSII the same ones which have been produced by lysis of water or were they simply floating around in the chloroplast?


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The Attempt at a Solution

 
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Yes, ATP is produced during the first step of the electron transport chain. The hydrogen ions are pumped into the thylakoid, creating a proton gradient, which allows ATP synthase to produce ATP using the potential energy. In PSI, each chlorophyll molecule loses only one electron, which is why two electrons must cycle the electron transport chain twice. The protons that are pumped into the thylakoid come from the lysis of water molecules, not from elsewhere in the chloroplast.
 

What is non-cyclic phosphorylation of photosynthesis?

Non-cyclic phosphorylation is the process by which plants and other photosynthetic organisms use light energy to produce ATP and NADPH, which are essential for the light-independent reactions of photosynthesis. This process occurs in the thylakoid membrane of chloroplasts.

How does non-cyclic phosphorylation differ from cyclic phosphorylation?

Non-cyclic phosphorylation involves both Photosystem I and Photosystem II, while cyclic phosphorylation only involves Photosystem I. Additionally, non-cyclic phosphorylation produces both ATP and NADPH, while cyclic phosphorylation only produces ATP.

What is the role of Photosystem II in non-cyclic phosphorylation?

Photosystem II absorbs light energy and uses it to split water molecules, releasing oxygen and protons. This process also produces electrons that are used to replace the ones lost by Photosystem I, allowing the photosynthetic process to continue.

What is the function of ATP and NADPH in non-cyclic phosphorylation?

ATP and NADPH are both energy-carrying molecules that are essential for the light-independent reactions of photosynthesis, also known as the Calvin cycle. ATP provides the energy needed for the reactions, while NADPH provides the electrons necessary for the reduction of carbon dioxide into glucose.

How is non-cyclic phosphorylation regulated?

The rate of non-cyclic phosphorylation is regulated by several factors, including the availability of light, the concentration of protons in the thylakoid lumen, and the activity of enzymes involved in the process. This ensures that the rate of ATP and NADPH production is balanced with the rate of their utilization in the Calvin cycle.

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