ZIMSEC O Level Combined Science: Photosynthesis

  • Green plants are the food and oxygen producers of the living world.
  • They manufacture organic molecules from inorganic raw materials.
  • Animals rely on green plants to make food that provides them with energy and oxygen.
  • Green plants are thus known as producers and animals are in turn known as consumers.
  • Only green plants can make food.
  • The process by which green plants make food from inorganic materials is known as photosynthesis.
  • Photosynthesis- is the process by which green plants use light energy to combine carbon dioxide and water into carbohydrates and releasing oxygen as a by product.
  • The word equation for photosynthesis is:
  • \text{Carbon Dioxide+Water}\xrightarrow[light]{chlorophyll}\text{Carbohydrates+Oxygen}
  • There are two types of carbohydrates made during the process of photosynthesis:
  • sugars and starch.
  • Testing for either of these molecules in plants will show whether plants are making food.
  • Most plants produce although others like cereals (e.g. maize) produce sugars first.
  • The simple sugar compound (glucose) is converted into starch for storage in the leaves.
  • Chlorophyll is the green pigment found in plants.
  • It is commonly found in plant leaves.
  • It absorbs light energy from the sun and converts it into chemical energy.
  • It absorbs light energy from the usn which can then be used to manufacture food.

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


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