Table of Contents
- 1 What is cyclic electron flow in photosynthesis?
- 2 What is PQ and PC in photosynthesis?
- 3 How important is the cyclic electron flow to the process of photosynthesis and to the cell?
- 4 What is happening during the light cycle?
- 5 How are cyclic and noncyclic electron flow different?
- 6 Why do the light reactions have both cyclic and noncyclic electron pathways?
What is cyclic electron flow in photosynthesis?
In cyclic electron flow (CEF), electrons are recycled around photosystem I. As a result, a transthylakoid proton gradient (ΔpH) is generated, leading to the production of ATP without concomitant production of NADPH, thus increasing the ATP/NADPH ratio within the chloroplast.
What is the flow of electrons in the light reaction?
In light reaction I, electrons are passed on to iron-sulfur proteins in the lamellar membrane, after which the electrons flow to ferredoxin, a small water-soluble iron-sulfur protein.
What is PQ and PC in photosynthesis?
The cytochrome complex, an enzyme composed of two protein complexes, transfers the electrons from the carrier molecule plastoquinone (Pq) to the protein plastocyanin (Pc), thus enabling both the transfer of protons across the thylakoid membrane and the transfer of electrons from PSII to PSI.
What happens in light reaction of photosynthesis?
During the light-dependent stage (“light” reactions), chlorophyll absorbs light energy, which excites some electrons in the pigment molecules to higher energy levels; these leave the chlorophyll and pass along a series of molecules, generating formation of NADPH (an enzyme) and high-energy ATP molecules.
How important is the cyclic electron flow to the process of photosynthesis and to the cell?
The light reactions in photosynthesis convert light energy into chemical energy in the forms of ATP and NADPH. The role of cyclic electron transport around PS I is proposed to be essential for balancing the ATP/NADPH production ratio and/or for protecting both photosystems from the damage via stromal over-reduction1.
How does cyclic differ from noncyclic electron flow?
In cyclic photophosphorylation, the electrons get expelled by photosystem I and they return to the system. On the other hand, in non-cyclic photophosphorylation, the electrons that are expelled by the photosystems do not return.
What is happening during the light cycle?
The light phase is the first phase of photosynthesis, when light is absorbed by complexes made up of chlorophylls and proteins called photosystems (located in the chloroplast). During this phase, solar energy is converted into chemical energy. This is of course photosynthesis.
Is cyclic electron flow light dependent?
Such cyclic flow generates DeltapH and thus ATP without the accumulation of reduced species. Whereas linear flow from water to NADP+ is commonly used to explain the function of the light-dependent reactions of photosynthesis, the role of cyclic flow is less clear.
How are cyclic and noncyclic electron flow different?
Cyclic photo-phosphorylation in photosynthesis light dependent reaction leads to the formation of ATP and NADPH, and the electrons go from water to PSII to PSI and eventually to NADPH. In non-cyclic photo-phosphorylation only some ATP is produced and the electrons go from PSII to PSI and back again.
How are the cyclic and non cyclic parts of the light reactions similar?
Similarities between cyclic and noncyclic phosphorylation Ø Both are dependent on light. Ø Both are electron transport systems. Ø Both pathways produce assimilatory powers. Ø In both phosphorylation and formation of ATP occurs.
Why do the light reactions have both cyclic and noncyclic electron pathways?
Both cyclic and non cyclic linear electron transport occur in higher plants chloroplast to maintain the required metabolic rate resulted in production of ATP and NADPH. The cyclic produces only ATP and no reducing powers.