What is photosynthesis?

Animals need to eat food to get their energy. But green plants and algae do not. Instead they make their own food in a process called photosynthesis. Almost all life on Earth depends upon this process. Photosynthesis is also important in maintaining the levels of oxygen and carbon dioxide in the atmosphere.

These are the things that plants need for photosynthesis:

  • carbon dioxide
  • water
  • light (a source of energy)

These are the things that plants make by photosynthesis:

  • glucose
  • oxygen

Here is the word equation for photosynthesis:

curriculum-key-fact
carbon dioxide + water → glucose + oxygen

Photosynthesis takes place inside plant cells in small objects called chloroplasts. Chloroplasts contain a green substance called chlorophyll. This absorbs the light energy needed to make photosynthesis happen. Plants and algae can only carry out photosynthesis in the light.

The plant cell is surrounded by a cell wall for structure. Inside this is the cell membrane and this contains the cytoplasm. There are chloroplasts and one nucleus in the cytoplasm, and in the centre of the cell is a large vacuoleA diagram of a plant cell to show its main components

Plants get carbon dioxide from the air through their leaves, and water from the ground through their roots. Light energy comes from the Sun.

The oxygen produced is released into the air from the leaves. The glucose produced can be turned into other substances, such as starch and plant oils, which are used as an energy store. This energy can be released by respiration.

The relationship between photosynthesis and respiration