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

General Photosynthesis Equation

Which means….

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

Lets take a closer look at this equation…

Six molecules of carbon dioxide and twelve molecules of water, are consumed, while glucose, six molecules of oxygen and six molecules of water 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 that is most widely used.

Simplified Photosynthesis Equation


  • 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 a oxygenic photosynthesis. There are some species of bacteria, however, that perform anoxygenic photosynthesis. This means that they consume carbon dioxide but do not release oxygen.

Want to learn more about Photosynthesis in Bacteria?

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