Since photosystem II occurs before photosystem I, why are they not named in reverse?

My answer:
Historically photosystem I was named one since it was discovered before photosystem II but this does not represent the order of the electron flow. Also, some bacteria that produce no oxygen during photosynthesis lack photosystem II. These results hints at the suggestion that the splitting of water is coupled to photosystem II and that photosystem I developed earlier in evolution.
if not can you add on to what i have
thanks!

Since this is not my area of expertise, I searched Google under the key words "photosystem I II" to get these possible sources:

http://en.wikipedia.org/wiki/Photosystem
http://student.ccbcmd.edu/~gkaiser/biotutorials/photosyn/ldr.html
(Broken Link Removed)

I hope this helps. Thaqnks for asking.

Explain Bot Explain Bot answered
9 months ago

To understand why photosystem II is named before photosystem I, we need to consider the historical discovery and chronological order of their identification.

Photosystem I was actually discovered first, hence the name. It was identified as part of the photosynthetic process in plants and algae, where it absorbs light energy and transfers electrons to produce NADPH (a molecule that carries high-energy electrons) and ATP (adenosine triphosphate, a molecule that stores energy).

Later on, scientists discovered that there is another photosystem, which they named photosystem II. This photosystem also absorbs light energy, but its primary function is to split water molecules, releasing oxygen as a byproduct and generating high-energy electrons that are then transferred to photosystem I.

The nomenclature of photosystem I and II might seem counterintuitive, as one would expect photosystem II to be named before photosystem I since it occurs first in the electron transport chain. However, the naming convention is based on the order of discovery rather than the chronological sequence in which they function.

It is important to note that not all photosynthetic organisms have both photosystems. Some bacteria, for example, lack photosystem II and can still carry out photosynthesis. This discrepancy further supports the notion that photosystem I likely existed before photosystem II in the course of evolutionary development.

In conclusion, the naming of photosystem I and II is based on their discovery order, not their chronological order in the photosynthetic process. The historical sequence of identification, along with the role of photosystem II in splitting water, suggest that photosystem I may have developed before photosystem II during the evolution of photosynthesis.