Where does non-cyclic photophosphorylation occur?

see full answer

Your Exam Success, Personally Taken Care Of

1:1 expert mentors customize learning to your strength and weaknesses – so you score higher in school , IIT JEE and NEET entrance exams.

An Intiative by Sri Chaitanya

(Unlock A.I Detailed Solution for FREE)

Best Courses for You

JEE

NEET

Foundation JEE

Foundation NEET

CBSE

Detailed Solution

Non-cyclic photophosphorylation occurs in the thylakoid membranes of chloroplasts. Inside green plant cells, chloroplasts have stacks of tiny discs called thylakoids. Their membranes hold the light-harvesting systems, photosystem II (PSII) and photosystem I (PSI). When both PSII and PSI operate together, electrons flow from water to NADP⁺, making ATP, NADPH, and oxygen.

This is called non-cyclic photophosphorylation and it happens on the thylakoid membrane surface (PSII mainly in grana; PSI more on stroma lamellae, but overall the site is the thylakoid membrane).

What happens there

PSII absorbs light: water splits (photolysis) → O₂ + H⁺ + e⁻.
Electron transport chain: electrons move through carriers; energy pumps H⁺ into thylakoid lumen.
ATP synthase: H⁺ flow back drives ATP formation (chemiosmosis).
PSI absorbs light: electrons are re-excited and reduce NADP⁺ to NADPH.

Feature	Non-cyclic	Cyclic
Photosystems used	PSII and PSI	Only PSI
Products	ATP, NADPH, O₂	ATP only
Electron path	Linear (H₂O → NADP⁺)	Electrons cycle back to PSI
Site	Thylakoid membranes	Thylakoid membranes