Photo system II is a large pigment-protein complex found in the thylakoid membrane of photosynthetic organisms that converts sunlight into chemical energy. It catalyzes the splitting of water molecules into protons, electrons, and oxygen to produce ATP and NADPH. Photo system II contains at least 99 cofactors including 35 chlorophyll a molecules, 12 beta-carotene molecules, and a manganese calcium oxide cluster that catalyzes the water-splitting reaction.

1. Protein complexes of
photo system II

2. Photo system II
Photo system II (PSII) converts sunlight into
chemical energy . Photo system II (PSII) is a large
pigment–protein complex embedded in the
thylakoid membrane of all oxygenic photosynthetic
organisms: Cyanobacteria, algae, and plants. In this
water molecules split into protons, electrons, and
molecular oxygen, ultimately yielding the high-
energy molecules ATP and NADPH . The water-
splitting reaction is catalyzed by a Mn4CaO5

3. • Photo system II contains at least 99 cofactors: 35
chlorophyll a, 12 beta-carotene, two pheophytin,
two plastoquinone, two heme, one bicarbonate, 20
lipids .
• Photo system II reaction center contains five
proteins D1, D2, PsbE, PsbF, and PsbI .
• Algae and higher plants have two photo system .
Photosynthesis bacteria have one photo system .

5. Reaction center consists
chlorophyll P680
plastoquinone
water
pheophytin
heme B
beta carotene

7. Subunit Family Function
D1
Photo synthetic
reaction center protein
family
Reaction center
protein , binds chl
P680 , pheophytin
,beta carotene ,
quinone and Mn
center
D2 Reaction center
protein
CP43
(B)
Photo system II light
harvesting protein
family
Binds manganese
center
CP47
(C)
O Manganese stabilizing
protein family
Manganese stabilizing
protein

8. cofactor / coenzyme Function
Chlorophyll Absorb light energy into chemical
energy
Beta carotene Quench excess photoexidation
energy
Heme B Secondary / protective electron
carrier
Plastoquinone Mobile intra thylakoid membrane
electron carrier
Manganese center Oxygen evolving center
Pheophytin Primary electron acceptor