Question

Photosystem I and II each have one central chlorophyll, which donates an electron to the ETC. why do both photosystems have additional chlorophylls surrounding the central chlorophyll and how do they work?

Answer 1

Answere : Light is captured by photosystems. Each photosystem is the a network of Chlorophyll A, Chlorophyll B, carotenoids and other accessory pigments.

It consists of two closely linked components :

1. REACTION CENTER - It made up of many central primary Chlorophyll A molecules.

2. ANTENNA COMPLEX - It is made up of hundreds of carotenoids and Chlorophyll B pigments molecules. Energy of electrons are transferred through the antenna complex to the reaction center

At the reaction center, the energy from the antenna complex is transferred to chlorophyll a.
This energy causes an electron from Chlorophyll to become excited.
The excited electron is transferred from Chlorophyll A to an primary electron acceptor.

Chlorophyll B absorbs blue light. Chlorophyll B play a central role to expand the absorption spectrum of organisms.

That way, organisms can absorb more energy from the higher frequency blue light part of the spectrum. The presence of chlorophyll B in cells helps organisms convert a wider range of the energy from the sun into chemical energy.

Having more chlorophyll B in chloroplasts of cells is adaptive. Plants that receive less sunlight have more chlorophyll B in their chloroplasts. An increase in chlorophyll B is an adaption to the shade, as it allows the plant to absorb a broader range of wavelengths of light. Chlorophyll B transfers the extra energy it absorbs to chlorophyll A.