Image credit arboday.org

Image credit arboday.org

ZIMSEC O Level Combined Science Notes: End products of photosynthesis and their fate

  • Green leaves manufacture starch or sugar during the photosynthesis process
  • Oxygen is also given out.
  • The oxygen passes out of the leaves by the process of diffusion.
  • It diffuses into the surrounding air.
  • There are microscopic holes/pores on the underside surface of leaves.
  • These pores are known as stomata (plural) or stoma (singular).
  • These pores allow carbon dioxide entry and oxygen to exit the leaf.
  • The carbohydrate(starch/sugars) molecules that are formed during the photosynthesis process are transported  to other parts of the plant.
  • Some parts of the plant have no chlorophyll and thus cannot photosynthesise.
  • Carbohydrates are transported as sugars as these molecules are soluble.
  • These sugars are transported from the leaves through microscopic tubes to the other parts of the plant.
  • This process of transportation is known as translocation.
  • The carbohydrates can either be used immediately to supply energy to the plant or they are stored.
  • If they are stored they are first converted into starch which is an insoluble compound.
  • Starch is stored in the leaves as a source of energy at night or in special organs.
  • Some seeds, fruits, roots and tubers for example potatoes contain large amounts of starch.
  • Carbohydrates may also be converted into structural molecules in the plant.
  • Cellulose is one such strong structural compound formed from carbohydrates.
  • It is used to make up cell walls in plants and helps to give plants support.
  • Cellulose makes up the fibrous parts of plants.
  • The fiber in plants like carrots, sugar cane and mangoes forms an essential part of human diet.
  • All this fiber comes is made up of cellulose.

To access more topics go to the Combined Science Notes page.


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