What Role Does Chlorophyll Play in Photosynthesis?

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Chlorophyll is the green pigment found most plentiful inside the leaves of plants. It is located within chloroplasts, where photosynthesis takes place.


Photosynthesis is the process by which plant life converts solar energy into high energy-yielding molecules to be used by the cells as needed. Chlorophyll plays a primary role in this process.


The chemical structure of chlorophyll consists of a porphyrin ring and a hydrocarbon side chain. In the center of the porphyrin ring is an atom of magnesium. The ring consists of alternating single and double bonds, which are usually found within molecules that are highly absorptive of visible light.

Chlorophyll a has a methyl group (CH3) attached to its ring, and chlorophyll b is distinguished by a carbonyl group (CHO).


There are three types of chlorophyll: chlorophyll a, which has pigments that absorb blue-violet and red light, participates directly in the light reactions of photosynthesis and is the most essential type of chlorophyll; chlorophyll b, which is similar to chlorophyll a although it participates in photosynthesis indirectly and absorbs blue and orange light; and carotenoids, which is the family of yellow-orange pigments and absorbs blue-green light.


The thylakoids are membranous sacs which are stacked (grana) inside of chloroplasts. The chloroplasts are the sites of photosynthesis, primarily in the light reactions. Chlorophyll is inside of the thylakoid membrane, and it’s where the energy from light is absorbed.

Photosynthesis occurs in two steps: light reactions and the calvin cycle. During the light reactions, energy from the sun is converted into chemical energy. That chemical energy is put into the calvin cycle, which takes in carbon dioxide (CO2) from the environment, converting it to glucose.


Chlorophyll b and carotenoids are actually “accessory pigments.” These pigments broaden the spectrum of available light that can be absorbed as they transfer energy to chlorophyll a.

Carotenoids play a role in protecting chlorophyll against damage from excess light.

About the Author

Aunice Reed is a medical science writer living in Los Angeles, Calif. With over 10 years previous nursing experience, Reed has been writing for over six years and has attended University of Northern Iowa, University of California, Los Angeles and Los Angeles Harbor College.

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