Where do the electrons come from in cyclic photophosphorylation?

This form of photophosphorylation occurs on the stroma lamella, or fret channels. In cyclic photophosphorylation, the high-energy electron released from P700 of PS1 flows down in a cyclic pathway.

Where do photosystem 1 electrons come from?

Photosystem I receives electrons from plastocyanin or cytochrome c6 on the lumenal side of the thylakoid membrane and uses light energy to transfer them across the membrane to ferredoxin on the stromal side. It can also function in a cyclic electron transport pathway.

When electrons are in a cyclic flow using photosystem I and P700 is oxygen produced is NADPH produced explain?

Under certain conditions, the photoexcited electrons take an alternative path called cyclic electron flow, which uses photosystem I (P700) but not photosystem II (P680). This process produces no NADPH and no O2, but it does make ATP. This is called cyclic photophosphorylation.

Where do electrons for photosystem 2 come from photosystems 1?

In (a) photosystem II, the electron comes from the splitting of water, which releases oxygen as a waste product. In (b) photosystem I, the electron comes from the chloroplast electron transport chain. The two photosystems absorb light energy through proteins containing pigments, such as chlorophyll.

Where is photosystem 1 found?

Photosystem I (PSI) is a multisubunit protein complex located in the thylakoid membranes of green plants and algae, where it initiates one of the first steps of solar energy conversion by light-driven electron transport.

What is produced in photosystem 1?

Photosystem I produces NADPH, which is similar in function to the NADH and FADH2 produced by the citric acid cycle. NADPH is an electron carrier that can donate electrons to other compounds and thus reduce them.

How are photosystem II and photosystem I in the chloroplast connected?

Plants have a chloroplast with thylakoid membranes—which consists of photosystems I (PSI) and II (PSII)—that are connected by the cytochrome b6f complex.

What electrons are produced from photosystem II?

The passage of electrons through photosystems I and II thus generates both ATP and NADPH, which are used by the Calvin cycle enzymes in the chloroplast stroma to convert CO2 to carbohydrates (see Figure 2.39).

What does photosystem 1 require?

The light reaction occurs in two photosystems (units of chlorophyll molecules). Photosystem I obtains replacement electrons from the electron transport chain. ATP provides the energy and NADPH provides the hydrogen atoms needed to drive the subsequent photosynthetic dark reaction, or Calvin cycle.

Where does the process of cyclic photophosphorylation take place?

This process usually takes place in the thylakoid membrane and uses Photosystem I and the chlorophyll P700. During cyclic photophosphorylation, the electrons are transferred back to P700 instead of moving into the NADP from the electron acceptor.

Where does photophosphorylation occur in the thylakoid membrane?

This type of photophosphorylation usually occurs in the thylakoid membrane. The electron begins in a pigment complex called photosystem I in cyclic electron flow. It then further passes from the primary acceptor to ferredoxin and eventually to cytochrome b6f.

What energy is used in photophosphorylation?

In photophosphorylation process, light energy is used to make a high-energy electron donor and a lower-energy electron acceptor. Electrons then move suddenly from donor to acceptor through an electron transport chain. ATP is produced by an enzyme called ATP synthase.

What is the difference between OXPHOS and photophosphorylation?

-Protons are pumped into the lumen of the thylakoid but out of the matrix of the mitochondria (IMS). -In OXPHOS, energy comes from reduced molecules being oxidized to make ATP. In photophosphorylation, energy comes from light to make ATP and reduced molecules (NADPH) are generated. – Ferredoxin transfers electrons to plastoquinone.