Question

Why are type I and type II reaction centers required for oxygeneic photosynthesis?

Answer 1

Two types of photosystems are embedded in the thylakoid membrane: photosystem I ( PSI) and photosystem Il (PSlI). Each photosystem plays a key role in capturing the energy from sunlight by exciting electrons. These energized electrons are transported by energy carrier molecules, which are responsible for light-independent reactions.

Photosystems consist of a light-harvesting complex and a reaction center. Pigments in the light-harvesting complex pass light energy to two special chlorophyll a molecules in the reaction center. The light excites an electron from the chlorophyll a pair passes to the primary electron acceptor. The excited electron will be replaced. In photosystem II, the electron comes from the splitting of water, which releases oxygen as a waste product. In photosystem I, the electron comes from the chloroplast electron transport chain.

These two photosystems oxidize different sources of the low-energy electron supply, pass their energized electrons to different places, and respond to different wavelengths of light.