What is photosynthesis?

Plants make their own food using photosynthesis. The food produced is the sugar called glucose. Food produced by plants is important, not only for the plants themselves, but for other organisms that feed on the plants.

Algae can also make their own food by the process of photosynthesis. Plant biomass will increase as a result of photosynthesis.

During photosynthesis, plants produce glucose and oxygen from carbon dioxide and water, using light energy from the Sun.

The following equations summarise what happens in photosynthesis:

Diagram illustrating the word and symbol equations for photosynthesis

\[\text{carbon dioxide} + \text{water} \xrightarrow[chlorophyll]{light} \text{glucose}+ \text{oxygen}\]

Be careful not to confuse this photosynthesis equation with respiration which is the reverse of this.

Photosynthesis is an endothermic reaction as it requires light energy to react carbon dioxide and water to produce glucose and oxygen.

The light energy required is absorbed by a green pigment called chlorophyll in the leaves. Chlorophyll is located in chloroplasts in plant cells.

Plant leaves are the main organ for photosynthesis.

The carbon dioxide required for photosynthesis comes from the air. It enters leaves through the stomata. Water enters the plant through the roots, and is transported to the leaves in the xylem.

Oxygen is formed as a product. Some is used for respiration. During the day, provided the rate of photosynthesis is high enough, plant and algae give out oxygen.

Some of the glucose produced by photosynthesis is used for respiration.

Glucose is the starting point for making the materials that plants need to live. These materials are used to make cell walls and other cell components and will enable the plant to growth and increase in biomass.

The glucose not used for respiration is used in the following ways:

An image showing the cycle of gluecose.