5 questions on "Metabolic Pathway of Microorganisms - Osygenic Photosynthesis"

What kind of reaction center do oxygenic phototrophs have?
The electrons flow through two distinct photosystems called photosystem I (P700) and photosystem II (P680). Photosystem I has an FeS-type reaction center and photosystem II a Q-type reaction center.
How does oxygenic photosynthesis work?
PSII performs the first step by splitting water into oxygen, hydrogen and electrons. This happens in the water-oxidizing complex and is catalyzed by Mn4Ca. Each electron travel through several proteins in the PSII photocomplex and two electrons are used to reduce PQ to PQH2, generating the proton motive force.
The electrons from PQH2 are transferred through cytochrome b6f and through plastocyanin donated to PSI reaction center. The electrons travel through PSI with the reduction of NADP+ to NADPH.
How many protons are translocated for every molecule of O2 produced by oxygenic photosynthesis?
12 protons
What kind of photophosphorylation does oxygenic photosynthesis use?
Noncyclic photophosphorylation, because electrons do not cycle back to reduce the oxidize P680, but is used in the reduction of NADP+. However, oxygenic phototrophs can perform cyclic photophosphorylation when the cell requires less NADPH.
When do oxygenic phototrophs use anoxygenic photosynthesis?
When PSII activity is blocked, oxygenic phototrophs can perform photosynthesis using only PSI. In these conditions, cyclic photophosphorylation occurs exclusively, and reducing power for CO2 comes from sources other than water.
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