Final answer:
Photosynthesis in plant cells converts sunlight energy into chemical energy stored in ATP and NADPH through light-dependent reactions involving chlorophyll, photophosphorylation, and chemiosmosis.
Step-by-step explanation:
Plant cells transfer energy from sunlight into the energy-carrying molecules ATP and NADPH through a process called photosynthesis. This process takes place mainly in the chloroplasts of plant cells, with the light-dependent reactions being the first stage.
When chlorophyll molecules within the chloroplast absorb sunlight, their electrons become excited to a higher energy state. These electrons are then transferred through a series of protein complexes known as the electron transport chain (ETC).
As the electrons move through the ETC, they power the pumping of hydrogen ions into the thylakoid space, creating an electrochemical gradient.
Hydrogen ions flow back through the protein complex ATP synthase via a process known as chemiosmosis, facilitating the phosphorylation of ADP to ATP, in a step called photophosphorylation.
Additionally, electrons that reach photosystem I are re-energized by sunlight and then used in the reduction of NADP+ to NADPH. These energy-carrying molecules, ATP and NADPH, store the solar energy in chemical bonds and later provide the energy for the synthesis of sugars in the Calvin cycle.