Question

How do plants get the energy to perform photosynthesis?

Answer 1

The photosynthesis process mainly requires light, carbon dioxide and the presence of chlorophyll pigment from plants. In photosynthesis, the sunlight helps in the synthesis of organic compounds which work as food for the plant.

Complete Answer:
Photosynthesis is simply a process where carbon dioxide and water get converted into sugar and oxygen molecules. Photosynthesis takes place in two steps one is the photochemical phase and the next is the biosynthesis phase. In the photochemical phase, the light energy gets absorbed in the harvesting zone and then gets transferred to its photo-centre. After getting sufficient quantum energy the photo-centre emits electrons and this electron with the high potential moves down into the electron transport chain with the formation of ATP.
In the biosynthetic phase, the photosynthesis process depends on the product of light reaction for fixation and reduction of carbon dioxide to form carbohydrates. This process takes place in the stroma of the chloroplast.
Both of these reactions show that for the reaction of photosynthesis to take place the energy comes from the light which is the sunlight that helps in the production of molecules by the breakdown of substrate molecules.

Additional Information:
For the light harvesting complex two photosystems are present, photosystem I and photosystem II. Each photosystem has a photo-centre or reaction centre which consists of 200 harvesting pigment molecules. The photo-centre consists mainly of chlorophyll a molecule and in PSI it has an absorption peak at 700nm whereas in PSII it has an absorption peak at 680 nm. The antenna and core molecule are part of the harvesting molecule in which the antenna absorbs the light of various wavelengths.

Note:
Photosynthesis is the only process by which green plants prepare food for the rest of the organism present in the environment.
In the case of absorption of light in antenna molecules of the light-harvesting complex the light that gets absorbed is of a shorter wavelength as compared to that of the photo-centre.