Why are pigments such as chlorophyll needed for photosynthesis

The chlorophyll pigment have photosystem 680/ PS I which captures the sunlight. Then the pigments gets excited and photosynthesis starts. Without chlorophyll photosynthesis can't happen.

Explanation:

Photosynthesis occurs in the chlorophyll pigment of the plant. They have the capacity to trap light energy and convert its energy to form glucose and oxygen.  

The chlorophyll is a double layer membrane structure. In it two photosystems works i.e. photosystem I and photosystem II. In the photosystem I light is trapped.  

In the chlorophyll thylakoids are present which have photosystem 680. It captures the photons coming from the sun. The photons are the light of different wavelengths which are absorbed by plants.  

The photon have more energy, and when it comes in contact with PS 680, the pigments get excited. Then they release high energy electrons which helps to form ATP, NADPH. Because it is a light dependent reaction.

Glucose and oxygen are formed in the stroma as it does not require light. It is a light independent reaction.

Therefore, chlorophyll is first require to capture photons coming from sun.