* Light energy is absorbed by chlorophyll: The chlorophyll pigment within chloroplasts absorbs light energy, primarily in the red and blue wavelengths of the visible spectrum.
* Energy transfer and electron excitation: This absorbed light energy excites electrons within the chlorophyll molecule, boosting them to a higher energy level.
* Production of ATP and NADPH: The energized electrons are passed along an electron transport chain, releasing energy. This energy is used to generate ATP (adenosine triphosphate) through photophosphorylation, and NADPH (nicotinamide adenine dinucleotide phosphate) is also produced.
* Water is split: Light energy also provides the energy needed to split water molecules, releasing oxygen as a byproduct.
In summary:
The light-dependent reactions are called so because they depend on light energy to perform their key functions:
* Absorbing light energy.
* Generating ATP and NADPH.
* Splitting water molecules.
These products (ATP, NADPH, and oxygen) are then used in the second stage of photosynthesis, the light-independent reactions (Calvin cycle).
