Page 78 - Medicinal Plants_PharmD general

Due to the separate location of the two photosystems in the thylakoid
membrane system, mobile electron carriers are required to shuttle electrons
between them (Figure 22). These carriers are plastoquinone and
plastocyanin.
Plastoquinone shuttles electrons from photosystem II to the cytochrome
b6f complex. It is lipid-soluble so moves within the thylakoid membrane.
Plastocyanin is a copper-containing protein that carries electrons from the
cytochrome b6f complex to photosystem I. It moves through thylakoid
lumen.
Cytochrome b6f is an integral membrane protein, of approximately 400
amino acid residues, that non-covalently binds two heme group Fe++ (two
iron atoms). Energetically, it is situated between the two photosystems and
transfers electrons from photosystem II-plastoquinone to plastocyanin-
photosystem I.

Figure 22. Electron transport chain in the Thylakoid membrane

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