What is chlorophyll ? The chlorophyll is a natural pigment present in  chloroplasts of  all photosynthetic cells of plants, algae , cyanobacteria and some protists .This pigment absorbs violet, blue and red light in the electromagnetic spectrum and reflects green light, that is, all organisms that have chlorophyll are green.

The amount of chlorophyll present and its distribution in each species is quite variable, so there are several different shades of green in these organisms.

Index [ hide ]

  • Where is chlorophyll found?
  • How is chlorophyll?
  • What is chlorophyll for?
  • How is light absorbed?
  • Other associated pigments

Where is chlorophyll found?

Chlorophyll can be found in all photosynthetic living beings on planet Earth, in greater concentration in the organs that show green color.

The molecules of this pigment are stored inside the chloroplasts, in internal membranes called thylacoids.

Together, chloroplast and chlorophyll, form a photosystem, where each has around 400 chlorophyll molecules.

How is chlorophyll?

The molecular structure of chlorophyll has four pyrrolic rings linked in the center by a magnesium atom. The magnesium atom is also linked to four hydrogen atoms and a long side chain of  alcohol.

The chemical formula is represented by:  55 H 72 O 5 N 4 Mg . Chlorophyll has  an unstable chemical structure and  is therefore easily degraded.

Chlorophyll – Chemical and structural formula

Chlorophyll can have four variations according to the position of the radicals in the molecule:

  • Green plants : chlorophyll  a  and  b
  • Algae and cyanobacteria : chlorophylls  c  and  d

Chlorophyll type  to  is the most abundant, with about 75% of the total chlorophyll. Chlorophylls  b,  c  and  d are considered accessory pigments that increase light absorption.

What is chlorophyll for?

This pigment is responsible for absorbing the energy of sunlight and transforming it into chemical energy through the process of  photosynthesis .

Chlorophyll – Energy absorption within chloroplasts (where chlorophyll is stored).

In addition, it has importance in the industry as it is used as a natural dye for food and cosmetics.

There is also research that indicates the effectiveness of using chlorophyll as an antioxidant.

How is light absorbed?

The light energy is absorbed through the electron excitation of chlorophyll. This absorption can happen in three ways, where chlorophyll leaves the highest energy level with excited electrons and returns to the lowest level.

  1. Total or partial conversion of energy to heat occurs.
  2. The energy is transferred from one excited chlorophyll molecule to another nearby, forming an excitation chain of molecules, in a process called resonance energy transfer.
  3. The excited electrons are passed on through an electron transport chain, thus transmitting the energy.

The photosynthesis process uses the last two forms of energy transfer. The energy is used in the photosystem in two different processes: antenna complex and reaction center.

In the antenna complex, energy is captured by the chlorophyll molecules and transferred by resonance to the reaction center.

The reaction center converts light energy into chemical energy through the loss of electrons from chlorophyll molecules.

This whole process of electron loss oxidizes the chlorophyll molecule, thus generating oxygen gas  (O )  at the end of photosynthesis.

Other associated pigments

There are other pigments that also absorb light in other spectra and have an accessory role in photosynthesis, transferring energy to it, they are: carotenoids and xanthoplasts.

Even if the plant is completely green, it probably has other pigments in smaller amounts than chlorophyll.

by Abdullah Sam
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