The thylakoid lumen is the compartment in the chloroplast bounded by the thylakoid membrane. It plays a vital role for photophosphorylation during photosynthesis. A thylakoid is a phospholipid bilayer membrane internal to chloroplasts. ... The first stage of the photosynthetic system is the light-dependent reaction, which converts solar energy into chemical energy. ... Leaf. ...

Chemiosmosis

During photosynthesis the lumen becomes acidic, as low as pH 4, compared to pH 8 in the stroma. This represents a 10,000 fold concentration gradient for protons across the thylakoid membrane. Thus, the chemiosmotic potential between the lumen and stroma is high enough to drive ATP synthesis using the ATP synthase. In this manner, the light-dependent reactions are coupled to the synthesis of ATP via the proton gradient. For alternative meanings see acid (disambiguation). ... Stroma can refer to: 1) The connective supportive framework of a biological cell, tissue, or organ. ... Properties In physics, the proton (Greek proton = first) is a subatomic particle with an electric charge of one positive fundamental unit (1. ... Electrochemical potential is a thermodynamic measure that reflects energy from entropy and electrostatics and is typically invoked in molecular processes that involve diffusion. ... Stroma can refer to: 1) The connective supportive framework of a biological cell, tissue, or organ. ... An ATP synthase (EC 3. ... The first stage of the photosynthetic system is the light-dependent reaction, which converts solar energy into chemical energy. ...

Source of proton gradient

The protons in the lumen come from three primary sources.

• Photolysis by photosystem II oxidises water to oxygen, protons and electrons in the lumen.
• The transfer of electrons from photosystem II to plastoquinone during non-cyclic electron transport consumes two protons from the stroma. These are released in the lumen when the reduced plastoquinol is oxidized by the cytochrome b6/f protein complex on the lumen side of the thylakoid membrane.
• The reduction of plastoquinone by ferrodoxin during cyclic electron transport also transfers two protons from the stroma to the lumen.

The proton gradient is also caused by the consumption of protons in the stroma to make NADH from NAD+ at the NADP reductase. Photolysis refers to any chemical reaction in which a compound is broken down by light. ... In the process of photosynthesis, light is absorbed by a photosystem (ancient Greek: phos = light and systema = assembly) to begin an energy-producing reaction. ... General Name, Symbol, Number oxygen, O, 8 Chemical series Nonmetals Group, Period, Block 16, 2, p Appearance colorless Atomic mass 15. ... Properties The electron is a fundamental subatomic particle that carries a negative electric charge. ... Plastoquinone Plastoquinone, often abbreviated pq, is a molecule used in the electron transport chain in the light-dependent reactions of photosynthesis. ... The first stage of the photosynthetic system is the light-dependent reaction, which converts solar energy into chemical energy. ... The cytochrome b6f complex (plastoquinol—plastocyanin reductase; EC 1. ... Plastoquinone Plastoquinone, often abbreviated pq, is a molecule used in the electron transport chain in the light-dependent reactions of photosynthesis. ... The first stage of the photosynthetic system is the light-dependent reaction, which converts solar energy into chemical energy. ...

Lumen specific proteins

The electron transport protein plastocyanin is present in the lumen and shuttles electrons from the cytochrome b6/f protein complex to photosystem I. Plastocyanin is a single strand protein of the thylakoid membrane, (molecular weight 10,500), that plays an integral part in photosynthesis. ...