Photosystem I and Photosystem II

What’s the difference between photosystem I and II? Which one comes first? I am not even sure if this is on the exam though.

Remember photo system 2 comes first. They were named after when they were discovered. Both are a part of the light-dependent reactions. I think that the electrons that the pigment molecules get after they are excited in Photo system II are from the hydrogen in the water molecules releasing oxygen as a by-product and the pigment in photosystem I gets their electrons from the electrons generated in Photosystem II after they’ve been through the ETC. PS1 is also called P700 because the pigment absorbs this wavelength of red light the best and same is for P680 (PSII)

Fiveable Logo

2550 north lake drive
suite 2
milwaukee, wi 53211



about for students for parents for teachers for schools & districts content team privacy contact


🥇 2020 Fiveable Olympics study plans upcoming events trivia hypertyper resources cram passes


community tiktok discord twitter instagram facebook careers

*ap® and advanced placement® are registered trademarks of the college board, which was not involved in the production of, and does not endorse, this product.

© fiveable 2020 | all rights reserved.