noncyclic electron flow

biology

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July 1, 2026

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Noncyclic electron flow is a crucial part of the light-dependent reactions in photosynthesis, occurring within the thylakoid membranes of chloroplasts. This process begins when pigments like chlorophyll absorb sunlight, exciting electrons. These energized electrons are then passed along an electron transport chain.12

This flow of electrons generates a proton gradient, which drives the synthesis of ATP, the cell's energy currency. Additionally, the electron flow reduces NADP+ to NADPH. To replenish the electrons lost by chlorophyll, water molecules are split in a process called photolysis, releasing oxygen as a byproduct and providing hydrogen ions for the proton gradient. Both ATP and NADPH are essential for the subsequent dark reactions, where sugars are produced.12

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photosynthesis
The pathway of electrons
…and intermediate carriers is called noncyclic electron flow. Alternatively, electrons may be transferred only by light reaction I, in which case they are recycled from ferredoxin back to the intermediate carriers. This process is called cyclic electron flow.
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…and intermediate carriers is called noncyclic electron flow. Alternatively, electrons may be transferred only by light reaction I, in which case they are recycled from ferredoxin back to the intermediate carriers. This process is called cyclic electron flow.
Read More