Pigment molecules absorb and transfer solar energy : Cooke’s Kokio - AskNature

Pigment molecules absorb and transfer solar energy : Cooke’s Kokio - AskNature: Pigment molecules in plants absorb and transfer solar energy using a special arrangement that funnels light toward a reaction center.The process of photosynthesis in plants involves a series of steps and reactions that use solar energy, water, and carbon dioxide to produce organic compounds. One of the first steps in this complex process depends on chlorophyll and other pigment molecules.

Chlorophyll is the green pigment molecule that makes plants appear green. In photosynthetic plant cells, chlorophyll molecules are embedded in stacked membranes (thylakoids) contained in special membrane-bound organelles called chloroplasts. The chlorophyll molecules are arranged in discrete units called photosystems, each of which contains hundreds of pigment molecules (chlorophyll plus others) arranged into an “antenna complex” surrounding a reaction center.

When light hits a pigment molecule in the antenna complex, the light energy “excites” the molecule, causing its electrons to jump to a higher level of energy. This excited state is temporary, and when the electrons fall back to a lower energy level, energy is released. This released energy can be transferred to a neighboring pigment molecule and so on, creating a chain of excited pigment molecules that ultimately deliver the energy to the photosystem’s reaction center. The reaction center contains special chlorophyll molecules that have a specific response to absorbing energy: rather than transferring only energy, the chlorophyll’s resulting high-energy electrons are transferred themselves to an electron-acceptor molecule, which begins the flow of electrons that plays a key role in the rest of photosynthesis.