Bitesize has changed! We're updating subjects as fast as we can. Visit our new site to find Bitesize guides and clips - and tell us what you think!
Print

Science

Photosynthesis

Page:

  1. 1
  2. 2
  3. 3
  4. 4
  5. 5
  1. Next

Plants make their own food by photosynthesis. Carbon dioxide and water react together in the presence of light and chlorophyll to make glucose and oxygen. The glucose is converted into starch, fats and oils for storage. It is used to make cellulose for cell walls, and proteins for growth and repair. It is also used by the plant to release energy by respiration.

Photosynthesis and respiration

Photosynthesis

Photosynthesis [photosynthesis: The chemical change that occurs in the leaves of green plants. It uses light energy to convert carbon dioxide and water into glucose. Oxygen is produced as a by-product of photosynthesis. ] is a chemical reaction that happens in the chloroplasts of plant cells. It produces glucose for use by the plant, and oxygen as a waste product. Here are the equations for photosynthesis:

Carbon dioxide + water Reaction (light energy, chlorophyll) glucose + oxygen

6CO2 + 6H2O Reaction (light energy, chlorophyll) C6H12O6 + 6O2

Light energy is absorbed by chlorophyll in the chloroplastschloroplast: Microscopic structure containing chlorophyl found in green plant cells where photosynthesis takes place. for photosynthesis to happen.

Respiration

It is not just animals that respire [respire: To engage in respiration - the energy-producing process inside living cells ] – plants carry out respiration as well. Plants respire all the time because their cells need energy to stay alive, but plants can only photosynthesise when they are in the light.

 

Time of dayPhotosynthesisRespiration
DayActiveActive
NightNoneActive

The diagrams summarise what this means for the overall release of carbon dioxide or oxygen from plants. Remember that respiration uses oxygen and produces carbon dioxide.

How plants affect the atmosphere: day

during the day plants photosynthesise and respire

Page:

  1. 1
  2. 2
  3. 3
  4. 4
  5. 5
  1. Next

Back to It's a green world index

BBC © 2014 The BBC is not responsible for the content of external sites. Read more.

This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.