Biology: Photosynthesis

Revision of topic 4: Photosynthesis & Plants

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Photosynthesis is the process where plants make food, sugar (glucose) from the gas carbon dioxide and water. It uses the energy in light trapped by the green pigment, chlorophyll which is found in structures called chloroplasts.


  • carbon dioxide enters via pores in the leaves called stomata
  • water enters the leaves in transport tissues in the veins. Water is also absorbed by specialised root cells called root hair cells


  • oxygen produced by photosynthesis diffuses out of the leaf if it is not required for respiration
  • Sugar is produced by this process and can be respired or converted to starch
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Testing for Starch

1. Place the leaf in boiling water for around ten seconds to kill it.

2. Boil the leaf in alcohol for around 5 minutes to remove the chlorophyll.

3. Dip in boiling water to soften it

4. Add iodine to test for starch

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Turkhan Baghirov


this is very useful thanks a lot

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