ATP produced - cyclic vs noncyclic

[PishPosh]

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I'm reading through Cliff's AP Bio, and it is saying that non-cyclic photophosphorylation produces 1.5 ATP for every 2e-, but in cyclic photophosphorylation only 1 ATP is produced for every 2e-. Could someone please explain why this is? Am I just misunderstanding something?

 

[Moka11]

I'm reading through Cliff's AP Bio, and it is saying that non-cyclic photophosphorylation produces 1.5 ATP for every 2e-, but in cyclic photophosphorylation only 1 ATP is produced for every 2e-. Could someone please explain why this is? Am I just misunderstanding something?

I've read somewhere that many times under standard conditions, even in the Noncyclic cycle, when electrons are going up from Ph-II to the primary electron acceptor, some will leak back into the cyclic cycle generating a bit more ATP. So the 1.5 may be counting the 1 from the first round on the electron transport chain, and the .5 may be the "bit more" from the leakage.