Video Transcript
The diagram provided shows a basic
outline of the light-dependent reactions. As electrons move from photosystem
two to photosystem one, how are they replaced? (A) By the reduction of NADP+, (B)
by the photolysis of water, (C) by the absorption of light energy, (D) by the
movement of H+ ions.
The light-dependent stage of
photosynthesis uses light energy to initiate a series of reactions, which eventually
results in the production of ATP. First, photosystem two absorbs
light energy, which excites the electrons contained within the chlorophyll pigment
in the photosystem. The electrons then move from one
structure of the electron transport chain to another. This means the electrons that were
transported from photosystem two need to be replaced.
When light energy is absorbed by
photosystem two, it’s used to excite electrons, but it’s also used to split water
molecules. Each water molecule is split into
oxygen, two hydrogen ions, and two electrons. The splitting of water using light
energy is called photolysis. The electrons produced by the
photolysis of water replace the electrons that move from photosystem two to
photosystem one. Therefore, our correct answer is
answer choice (B). The electrons are replaced by the
photolysis of water.
