Final answer:
Plants gain energy for photosynthesis by absorbing solar energy through chlorophyll during the light-dependent reactions. This energy is transformed into chemical energy, specifically ATP and NADPH, which are used in the Calvin Cycle to synthesize glucose.
Step-by-step explanation:
Energy for the photosynthesis reaction is gained by plants primarily through the light-dependent reactions. During these reactions, chlorophyll in the thylakoid membranes of the chloroplasts absorbs solar energy, which is necessary for the process of photosynthesis.
The absorbed light energy is then converted into chemical energy in the forms of ATP (adenosine triphosphate) and NADPH (nicotinamide adenine dinucleotide phosphate). This conversion is crucial because ATP and NADPH serve as energy carriers that transport energy to the second stage of photosynthesis known as the Calvin Cycle. In the Calvin Cycle, the stored chemical energy from these carriers is used for the synthesis of glucose from carbon dioxide.
Moreover, during the light-dependent reactions, water molecules are split in a process known as photolysis, releasing oxygen as a byproduct. This phase of photosynthesis, which includes the use of light energy, production of oxygen, and the generation of energy carriers, underscores the importance of sunlight in the formation of glucose and ultimately the storage of energy in the form of carbohydrates.