Overview of Photosynthesis


Light EnergyWord Origin

From the Greek: photo, “light”, and synthesis, “putting together”.

Definition of Photosynthesis

Photosynthesis is the process by which green plants, algae and some forms of bacteria use energy from sunlight to convert carbon dioxide and water into glucose.

General Equation for Oxygenic Photosynthesis

Let’s start with this equation and then you will see the simplified version in a minute.

General Photosynthesis Equation

The equation above shows….

carbon dioxide + water + light energy ——> glucose + oxygen + water

Let’s take a closer look at this equation…

Overall, six molecules of carbon dioxide (6CO2) and twelve molecules of water (12H2O) are consumed, while one molecule of glucose (C6H12O6), six molecules of oxygen (6O2) and six molecules of water (6H2O) are produced.

The equation above shows that water is both a reactant and a product of photosynthesis. Because twelve molecules of water are consumed and six molecules of water are produced, the equation can be simplified as shown below.  This is the equation for photosynthesis that is most widely used.

Simplified Photosynthesis Equation

This simplified balanced equation shows that six molecules of carbon dioxide (6CO2) are combined with six molecules of water (6H2O), using energy from sunlight, to produce one molecule of glucose (C6H12O6) and six molecules of oxygen (6O2).


  • carbon dioxide
  • water
  • sun’s energy


  1. Light dependent Reactions
  2. Calvin Cycle


  • glucose
  • oxygen

Want to learn more about the reactants, process and products of Photosynthesis?

Oxygenic vs. Anoxygenic Photosynthesis

Organisms capable of synthesizing their own food from inorganic substances, using sunlight as a source of energy are called Photoautotrophs. Most photosynthetic organisms or photoautotrophs, absorb carbon dioxide and produce oxygen. This is known as oxygenic photosynthesis. There are some species of bacteria, however, that perform anoxygenic photosynthesis. This means that they consume carbon dioxide but do not produce oxygen.

Want to learn more about Photosynthesis in Bacteria?


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