Simple Explanation of Photosynthesis

By David Chandler
Image by, courtesy of Anita Martinz

Photosynthesis is the process by which plants and some single-celled organisms produce sugars from sunlight and carbon dioxide. These sugars then become the food used in cellular respiration. In plants, photosynthesis occurs in specialized structures known as chloroplasts.


The overall reaction of photosynthesis utilizes six carbon dioxide molecules and six water molecules to produce one sugar molecule (glucose) and six oxygen molecules.

Photosynthetic Pigments

Photosynthetic pigments include chlorophylls, carotenoids and xanthophylls. These pigments are each sensitive to a particular range of light wavelengths.


Eukaryotic cells perform photosynthesis in a specialized, double-membraned structure called the chloroplast. The chloroplast contains a stacked series of membranes known as the thylakoid. Stack of thylakoids are called grana with the intermembrane space between thylakoids called the stroma.

Light Dependent Reactions

When light strikes photosensitive pigments such as chlorophyll, the electrons enter a high energy state. Through a series of electron transports, the energy from these excited electrons is utilized to create adenosine triphosphate (ATP) and nicotine adenine dinucleotide phosphate (NADPH). This process is known as photophosphorylation and occurs in the grana.

Light Independent Reactions

The high energy bonds produced during the light dependent reactions are used to create carbon-carbon bonds from carbon dioxide. This process, sometimes referred to as the Calvin Cycle, involves a multi-step series of enzymatic reactions to create a glucose sugar molecule from the addition of the carbon from a carbon dioxide molecule to a starter molecule called ribulose bisphosphate.

About the Author

David Chandler has been a freelance writer since 2006 whose work has appeared in various print and online publications. A former reconnaissance Marine, he is an active hiker, diver, kayaker, sailor and angler. He has traveled extensively and holds a bachelor's degree from the University of South Florida where he was educated in international studies and microbiology.