AP BIOLOGY

Detailed explanation-1: -The light-dependent reactions of photosynthesis take place within the thylakoids. These reactions occur when the pigment chlorophyll, located within the thylakoid membranes, captures energy from the sun (photons) to initiate the breakdown of water molecules.

Detailed explanation-2: -There are two types of photosystems in the light-dependent reactions, photosystem II (PSII) and photosystem I (PSI).

Detailed explanation-3: -The light-dependent reactions begin in photosystem II. In PSII, energy from sunlight is used to split water, which releases two electrons, two hydrogen atoms, and one oxygen atom.

Detailed explanation-4: -Photosystem I (PSI) is also capable of absorbing light energy. Electrons from its reaction center pigment P700 are transferred to the protein ferredoxin, which can then donate the electrons to the electron carrier NADP+ to form NADPH or to the electron transport chain resulting in the production of additional ATP.

Detailed explanation-5: -1: Light-dependent reactions harness energy from the sun to produce chemical bonds, ATP, and NADPH. These energy-carrying molecules are made in the stroma where carbon fixation takes place as part of the light-independent reactions (Calvin cycle).