Question

Please explain what photsyetems 1 and 2 are and it’s jobs

Answer 1

The photosynthesis can be dived into light and dark reaction, in light reactions the light energy is absorbed and used to produce NADPH2, and ATP which give energy to drive carbohydrate synthesis in dark reaction from Co2. In light-dependent reactions of photosystems, photosystems absorb light and excite their electrons and transfer them to reduce NADPH2. Basically, these are protein complexes found in thylakoid membranes of cyanobacteria, algae and plants. The photosystem 1 and 2 named due to their order of discovery, despite the fact that photosystem 2 respond first in light absorption.

Photosystem 2: It has a peripheral antenna system and a reaction center P680. The antenna system composed of light harvesting pigments and chloroplast which absorb light and transfer it to the photosynthetic reaction centre. The reaction centre excites at 680nm and transfers its electrons to the plastoquinone. which upon donate electrons to cytochrome to the PS1. It regains its lost electrons by splitting of water into O2.  

Photosystem 1: It also has the antenna complex which absorbs the light and a reaction center which excites at 700nm. It donates its electrons to NADPH2 through other complexes i.e Phylloquinone, iron-sulfur protein, ferredoxin, plastocyanin.

Photosystem 1 also involved in cyclic photophosphorylation where the excited electrons will not reach NADPH2 but they can produce proton motive force which synthesises ATP.