Photosynthesis involves several key events: absorption of light energy by chlorophyll, conversion of light energy to chemical energy (splitting of water), and the reduction of carbon dioxide to carbohydrates. These events lead to the production of glucose, which plants use for energy.
Elaboration:
1. Light Absorption:
Chlorophyll, the pigment in plants, absorbs light energy, primarily in the red and blue wavelengths. This absorbed energy is used to excite electrons within the chlorophyll molecule.
2. Light-Dependent Reactions:
Water Splitting (Photolysis): Light energy is used to split water molecules, releasing oxygen as a byproduct and providing electrons for the next stages.
ATP and NADPH Production: The energy from the light-dependent reactions is used to produce ATP (adenosine triphosphate) and NADPH (nicotinamide adenine dinucleotide phosphate), which are energy-carrying molecules.
3. Light-Independent Reactions (Calvin Cycle):
Carbon Fixation: Carbon dioxide from the atmosphere is taken in through stomata (pores on the leaf surface) and fixed (converted) into a three-carbon molecule.
Sugar Synthesis: ATP and NADPH from the light-dependent reactions are used to convert the three-carbon molecule into glucose. Glucose is then used as energy or stored as starch.
In essence, photosynthesis transforms light energy into chemical energy stored in the bonds of sugar molecules.