What Light dependent reactions?

Answer 1

Because the question does not ask photosynthesis, I answer in the meaning of general chemistry:

Light just provides energy for a reaction; usually, photons (the light particles) make electrons of the matter to excitate, thus changing the reaction conditions.

Otherwise, in photosynthesis, light-dependent reactions produce a proton (H+) gradient flow through thylakoid membrane, thus spinning the ATPase enzyme subunits, thus producing ATP. Besides this, ferredoxin and NADPH is produced. Ferredoxin is very important for certain specific enzymatic reactions and NADPH is the carrier of reduction force (it can give a hydrogen to a chemical/metabolite, for example to malonic acid)

Answer 2

Light dependent reactions start with absorption of photons by chlorophyll and cyclic and noncyclic phosphorylation takes place to enerzige the chlorophyll pigments and this ultimately results into photolysis of water in to H+ and OH- ions. The OH- ions being quite unstable gets converted into O2 and 2H+. The energy thus released is added to chemical compunds used in assimilation of CO2 during dark reactions.

Answer 3

The light-depenedent reactions produce oxygen gas and convert ADP and NADP+ into the energy carriers ATP and NADPH.

Textbook. ^-^

Answer 4

You need to open your textbook.