The Z-scheme or non-cyclic photosynthetic processes explain the electron transport system from photosystem-I to photosystem II via the electron shuttles.

Answer 1

In the Z-scheme or non-cyclic photosynthetic processes, the electron transport system describes the movement of electrons from photosystem I (PSI) to photosystem II (PSII) through a series of electron shuttles.

Initially, in PSII, light energy is absorbed by chlorophyll pigments, exciting electrons within the reaction center. These energized electrons are then captured by the primary electron acceptor molecule of PSII, leaving the reaction center positively charged. To replenish the lost electrons, water molecules are split, releasing oxygen gas, protons (H+ ions), and new electrons.

The energized electrons are passed down a series of electron carriers or shuttles, including plastoquinone and plastocyanin, to reach PSI. Plastoquinone accepts the electrons from PSII and transports them to the cytochrome b6f complex. Along this electron transport chain, protons are pumped across the thylakoid membrane and create a proton gradient, which is crucial for ATP synthesis later on.

After reaching the cytochrome b6f complex, the electrons are transferred to plastocyanin, which carries them to PSI. At PSI, another reaction center absorbs light energy, exciting electrons and generating new electron vacancies. The electrons from plastocyanin are then transferred to the primary electron acceptor of PSI.

To complete the non-cyclic process and maintain electron flow, the electrons from PSI are replenished by the oxidation of electron carriers, such as ferredoxin and NADPH. The electrons are eventually used to reduce NADP+ to NADPH, which is an electron carrier that plays a crucial role in the Calvin cycle, where carbon fixation occurs.

Overall, the Z-scheme or non-cyclic photosynthetic processes describe the flow of electrons from water to NADPH, driven by light energy, through a series of electron shuttles. This process generates ATP and NADPH, essential for the production of carbohydrates during the Calvin cycle.