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…