Which event occurs in photosystem i?

a. water molecules are broken apart.
b. light energy excites electrons.
c. oxygen is released as waste.
d. electrons are transferred to ferredoxin.

Answer B and D.

Photosystems are complexes made of proteins and light absorbing pigments. There are two types of photosystems, photosystem I (PSI) and photosystem II (PSII). Both the photosystems are involved in light reaction of the photosynthesis.

Photosystem I (PSI) absorbs photon of wavelength of 700 nm. The chlorophyll of PSI gets excited on receiving photon of wavelength of 700 nm.  The excited electron is transferred to a set of 4Fe-4S clusters. From this clusters the electron is transferred to the electron carrier called ferredoxin (Fd).  

The correct answers would be  

B. Light energy excites electrons.

D. Electrons are transferred to ferredoxin.

Photosystem I or P₇₀₀ is the second photosystem of the photosynthesis.

In this complex, chlorophyll a or P₇₀₀ reaction center absorb lights of wavelength 700 nanometer or higher. It uses this energy for photoexcitation, that is, the release of electrons through light energy.

The electrons are then passed on to the ferredoxin which helps in the reduction of NADP⁺ to NADPH.

answer; hypnagogic sensations)