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Harvesting The Sun

  • Plants capture energy from sunlight, many complex chemical reactions are involved. 
  • Plants use energy from sunlight to build up carbon dioxide and water into organic compounds such as glucose, this is the process of Photosynthesis.
  • Energy from the sunlight is transferred to chemical energy in the new compounds, So these compounds act as an energy store. 
  • They can be used as food molecules which are broken down to release energy, they also provide raw materials to build new plant cells for growing.
  • Living things that can make their own food are called Autotrophs.
  • Organisms that rely on other living things for food are called Heterotrophs.

Trapping Light Energy

  • Less than one-billionth of the sun's energy reaches the plants on earth.
  • Plants only convert only about 1-3% of this light energy into new plant material.
  • 60% of the light is the wrong wavelength for photosynthesis.
  • 5% Passes straight through the plant.
  • 35% is absorbed by the chloroplasts.
  • 2% is transferred to organic materials.
  • 33% is transferred as waste heat.
  • The chemical equation for photosynthesis: 

6Co2 + 6H2O => C6H12O6 + 6CO2

  • A glucose molecule is made up of carbon, hydrogen, and oxygen atoms. So glucose is a carbohydrate.
  • Photosynthesis takes place in Chloroplasts, they contain a green pigment called chlorophyll.
  • Chlorophyll absorb light and uses the energy to kick start photosynthesis. 
  • The light energy splits water molecules into hydrogen and oxygen atoms. 
  • The hydrogen is combined with carbon dioxide from the air to make glucose.
  • The oxygen is released as a waste product, it passes out of the plant and into the air.
  • Given enough raw materials, light, and the right temperature, a large tree can ,make 2000kg of glucose a day.

Using glucose from photosynthesis

  • Like all larger living things, plants are made up of different types of cells, but every cell is made up of the same basic chemicals:
  • Cell wall: Made of cellulose- a carbohydrate.
  • Membrane: Made…


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