Explain the overall purpose of the light dependent reactions?

Answer 1

The light dependent reactions get things ready for the Calvin cycle -- ATP and NADPH -- providing energy and hydrogen ions for the Calvin cycle to use.

Answer 2

These reactions take place in the thylakoid membranes. They involve 2 sets of light -absorbing reactions and 2 sets of electron transport chain reactions.

Step 1 (purpose 1): Light hits Photosystem II (P 680) causing electrons to be boosted to a higher energy level and pass into an electron transport chain. As a result some of the H+ from the stroma are carried through the thylakoid membrane and released into the space inside. ATP is produced here. ATP is needed to power the Calvin cycle later on.

Step 2 (purpose 2): at the end of the chain a low energy electron enters Photosystem I (P- 700). Here it gets energized by more sunlight. This energizes the electrons and moves them into the NADPH electron chain. This chain passes electrons to NADP+ in the stroma. Each NADP+ accepts 2 electrons and reacts with a H+
in the stroma to form NADPH. The result is to move the electrons out of the thylakoid into the stroma. These electrons are replaced by the splitting of water, that also produces H+ and O2. The H+ stays in the thylakoid and becomes part of the H+ reservoir that will power the chemiosmotic synthesis of ATP. The oxygen leaves the chloroplast and enters the atmosphere.

Answer 3

Light dependent reactions convert solar energy into chemical energy.

Example: photosynthesis