Photosynthesis

As plants are producers (autotrophs), they use carbon dioxide, water and light energy from the Sun to produce their own food, in a process called photosynthesis.

Photosynthesis takes place in subcellular structures called chloroplasts, which are located in the leaves. Chloroplasts contain a pigment called chlorophyll that gives plants their green colour and helps them absorb light. Plants use light energy from the Sun to convert carbon dioxide and water into glucose and oxygen.

The word and balanced symbol equation for photosynthesis are:

The carbon dioxide required for photosynthesis enters the leaf through the stomata. The roots absorb water via osmosis and the xylem transport this water to the leaf for photosynthesis.

There are many chloroplasts (containing chlorophyll) in the palisade cells, which maximises the absorption of light energy. Leaves are the main photosynthetic organs. However, other green parts of the plant that contain chlorophyll can also perform photosynthesis.

As photosynthesis requires an input of energy from sunlight and doesn’t release it all back, it is considered an endothermic reaction.

Some of the oxygen produced by photosynthesis is used for respiration and the rest diffuses out of the stomata. The glucose formed is used for many biological processes, including the production of other important molecules and for cellular respiration.

Do not confuse photosynthesis with respiration. On a simplified level, photosynthesis and respiration are opposite processes. The reactants of photosynthesis are the products of cellular respiration, and vice versa.

You’ve used 8 of your 10 free revision notes for the month

Sign up to get unlimited access to revision notes, quizzes, audio lessons and more

Sign up