light absorption by chlorophyll

Light absorption by chlorophyll

Chlorophyll is the chief light absorbing molecule

Absorption of light by the photosynthetic pigments such as chlorophyll is the very first event in the photosynthesis. Alternating single and double bonds (polyenes) in the chlorophyll are very efficient in absorbing various bands of visible light. When a chlorophyll molecule absorbs light, photons from light excites an electrons from its ground level of energy to an excited energy level. This excited molecule may return its electron back to ground level in various ways.

Light absorption by chlorophyll

1. Chlorophyll can release its energy by producing heat

Excited electron of chlorophyll can return into its ground level of energy by releasing the absorbed energy in the form of heat.

2. Chlorophyll can release its energy by fluorescence

Excited electron of chlorophyll can return into its ground level of energy by releasing the absorbed energy in the form of radiation of longer wavelength than its has absorbed, a phenomenon called as fluorescence.

3. Chlorophyll can transfer its energy through inductive resonance

In other way excited electron of chlorophyll can return into its ground level of energy by transferring its energy to a neighboring chlorophyll molecule by a physical method so-called inductive resonance. This phenomenon has the key role in harvesting of light and transferring energy to the reaction center.

4. Chlorophyll can transfer its energized electron to an electron acceptor

The excited chlorophyll can transfer its excited electron to a neighboring electron acceptor molecule, thus creating a charge separation so called photoinduced charge separation. This separation of charge takes place in the reaction center. This process is the driver of light reaction.