The relationship between photosynthesis and respiration

Different organisms have different methods of obtaining food.

For example:

1. Autotrophic organisms like plants and algae produce their own food through photosynthesis.
2. Heterotrophic organisms like animals obtain their food by eating other organisms.

Photosynthesis

Photosynthesis captures light energy to make glucose from carbon dioxide and water.

Overall photosynthesis equation:

6CO₂ + 6H₂O + light energy → C₆H₁₂O₆ + 6O₂

Respiration

Cellular respiration breaks down respiratory substrates like glucose, releasing energy that is temporarily stored in the form of ATP.

Overall respiration equation:

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + energy

The products of photosynthesis, glucose and oxygen, can be used as reactants in respiration to synthesise ATP. The products of respiration, carbon dioxide and water, can then be used as reactants in photosynthesis.

Key stages of photosynthesis

There are three main stages in photosynthesis:

1. Capturing of light energy - This is done by pigments such as chlorophyll.
2. The light-dependent reaction - This is when light energy is converted into chemical energy.
3. The light-independent reaction - This is when sugars and other organic molecules are produced.