Final answer:
The light reactions in photosynthesis involve the absorption of light energy by chlorophyll in the thylakoid membranes of the chloroplast. Water is used as a source of electrons, and oxygen is produced as a byproduct. ATP and NADPH are generated through two electron transport chains.
Step-by-step explanation:
The light reactions in photosynthesis involve the absorption of light energy by chlorophyll in the thylakoid membranes of the chloroplast. This energy is transferred to ATP and NADPH through two electron transport chains. Water is used as a source of electrons, and oxygen is produced as a byproduct. The electrochemical gradient formed in the process is utilized to generate ATP through chemiosmosis.