Plastoquinone

  Plastoquinone, (often abbreviated PQ), is a quinone molecule involved in the electron transport chain in the light-dependent reactions of photosynthesis. Plastoquinone is reduced (accepts two protons (H⁺) from the stromal matrix of the chloroplast, coupled to two electrons (e^-) from photosystem II), forming plastoquinol. It transports the protons to the lumen of thylakoid discs, while the electrons continue through the electron transport chain into the cytochrome b₆f protein complex.  

References

• Berg, J; Tymoczko, J; Stryer, L (2002). Biochemistry (Fifth Edition). W H Freeman and Company. ISBN 0716746840.