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Noncyclic electron flow assessment
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- SBI4U
- Institution
- 12th Grade
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2) The electrons that were lost by the P680 molecule are replaced by an enzyme protein, thisprotein called a Z protein. This protein splits a water molecule into oxygen, two hydrogen ions,
and electrons. The electrons that were released by the protein are now used to give to P680.
3) Light is the only mode of transport in which electrons travel; these electrons will travel in the
photon of light (Britannia); when the photon of light hits photosystem II, the primary electron
acceptor quickly snatches the electron. An enzyme protein called Z protein splits a water
molecule into oxygen, 2 hydrogen ions and electrons. The oxygen ion that was released
immediately grabs a partner and makes molecular oxygen.
4) The cytochrome b6f complex (plastoquinol—plastocyanin reductase) is an enzyme found in
the thylakoid membrane in chloroplasts of plants, cyanobacteria, and green algae, that catalyzes
the transfer of electrons from plastoquinol to plastocyanin. The reaction is analogous to the
reaction catalyzed by cytochrome bc1 (Complex III) of the mitochondrial electron transport
chain. During photosynthesis, the cytochrome b6f complex is one step along the chain that
transfers electrons from Photosystem II to Photosystem I, and at the same time pumps protons
into the thylakoid space, contributing to the generation of an electrochemical (energy) gradient
that is later used to synthesize ATP from ADP.
5) The role of the two re-energized molecules is to head to the NADP reductase enzyme, this
enzyme takes the two electrons, and together with a hydrogen atom from the stroma, it reduces
NADP+ to NADPH.
6) As the electrons pass down this first electron transport chain, they phosphorylate a molecule
of ADP to ATP. Phosphorylating an organic molecule means sticking a phosphate group onto it,
this causes it to become more unstable thus making it usable as an energy source. Noncyclic
photophosphorylation is harnessing the energy of light (photo) to phosphorylate a molecule of
ADP into ATP. The chemical ATP energy produced at this step is used during the next part of
photosynthesis, the Calvin Cycle, to make sugars.
References:
B. The pathway of electrons. from
https://www.britannica.com/science/photosynthesis/The-pathway-of-electrons#ref366145
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