Question

Which process in the light-dependent reactions results in the release of hydrogen ions, electrons, and oxygen? A) chemiosmosis B) photophosphorylation C) water splitting D) electron transport

Answer 1

Answer:

The correct answer is C) water splitting

Explanation:

During photosynthesis light energy is used to splits the water molecule into 2H⁺,1/2 O₂ and 2 e⁻. This process is called photolysis because in this process the lysis of water molecules takes place by photon energy.

Then the electrons are transferred to the photosystem to replace the excited electrons. This movement of electrons through the electron transport chain in the thylakoid membrane helps in pumping of H ion in thylakoid space from stroma against their concentration gradient.

So when the H ions go back in stroma through ATP synthase it generates ATP which is used for carbon fixation during photosynthesis. Therefore water splitting is the light-dependent reaction results in the release of hydrogen ions, electrons, and oxygen.

Answer 2

The right answer is D) electron transport.

In chloroplasts, light is used to oxidize water to oxygen, and to reduce NADP + to NADPH on the other hand, with concomitant proton injection into the lumen of thylakoids.

H2O ==> photosystem II (P680) ==> plastoquinone ==> cytochrome b6f complex ==> plastocyanin ==> photosystem I (P700) ==> ferredoxin ==> ferredoxin-NADP + reductase ==> NADP +