Why in ETC does PS2 go before PS1?
closed as unclear what you're asking by canadianer, James, David, The Last Word, kmm Nov 16 '18 at 20:55
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If your question is related to numbering, the photosystems were named in the order of their discoveries not participation.
In cyclic ETS PS-II doesn't participate at all.
PS-I would have gone first if PS-II was named PS-I.