Courses
Courses for Kids
Free study material
Offline Centres
More
Store Icon
Store
seo-qna
SearchIcon
banner

How does cyclic electron flow differ from non cyclic electron flow?

Answer
VerifiedVerified
476.1k+ views
like imagedislike image
Hint: Light reaction in the photo system starts electron flow. In oxygenic photosynthetic organisms, flow of electrons is of two types: non-cyclic as well as cyclic. Non-cyclic electron flow begins with the absorption of a photon by PSII. Cyclic electron flow begins with the absorption of a photon by PSI.

Complete answer:
Noncyclic electron flow: It is a light induced electron transport from water to NADP+ and a concomitant evolution of oxygen. It involves a collaboration of two photosystems: PSII and PSI. Electrons move from water through PSII to PSI and then to NADP+. Electron transport leads to generation of a proton-motive force and synthesis of ATP. Formation of ATP due to light induced non-cyclic electron flow is called non-cyclic photophosphorylation.

Cyclic electron flow: In certain cases, photoexcited electrons flow cyclic path, which involves PSI but not PSII. In cyclic electron flow, photoexcited electrons from P700 of PSI move through the b6f complex and back to P700. This cyclic electron flow is coupled to protons pumping into the thylakoid lumen. When protons flow down their electrochemical gradient through ATP synthase complexes, ATP synthesis occurs. The formation of ATP due to light-induced cyclic electron flow is called cyclic photophosphorylation. There is no production of NADPH and no release of oxygen in cyclic electron flow.

Non - cyclic electron flowCyclic electron flow
Both PSI and PSIIOnly PSI
Photolysis of waterNo photolysis of water
Formation of oxygenNo oxygen formation
ATP synthesis occursATP synthesis occurs
NADPH synthesis occursNo NADPH synthesis


Note: In cyclic electron flow photoexcited electrons from PSI are returned from ferredoxin to P700 via the cytochrome complex and plastocyanin. This electron flow generates electrochemical proton gradient and thus ATP but produces no NADPH.
Latest Vedantu courses for you
Grade 10 | MAHARASHTRABOARD | SCHOOL | English
Vedantu 10 Maharashtra Pro Lite (2025-26)
calendar iconAcademic year 2025-26
language iconENGLISH
book iconUnlimited access till final school exam
tick
School Full course for MAHARASHTRABOARD students
PhysicsPhysics
BiologyBiology
ChemistryChemistry
MathsMaths
₹36,600 (9% Off)
₹33,300 per year
Select and buy