photosynthesis

• Photosynthesis


  1. Takes place in leaves

  2. Takes place in chloroplasts

  3. Chlorophyll absorbs light

  4. Converts carbon dioxide and water into glucose and oxygen
• Photosynthesis requires light energy
• Endothermic reaction


  Reaction where energy is transferred from the environment
• How plant gets reactants for photosynthesis

  1. Carbon dioxide diffuses into leaves through stomata

  2. Water is taken up from soil by roots and transported to leaves via xylem
• Products of photosynthesis


  • Glucose is essential
  • Oxygen is also produced but not as important
• Uses of glucose


  • Cellular respiration
  • Making cellulose
  • Making starch
  • Making amino acids
  • Making oils and fats
• Plant growth rate often depends on rate of photosynthesis
• Factors affecting rate of photosynthesis are light intensity, temperature, carbon dioxide concentration, and amount of chlorophyll
• Factors affecting photosynthesis


  • Light intensity
  • Temperature
  • Concentration of carbon dioxide in the air
  • Amount of chlorophyll in plants
• Chlorophyll


  Pigment within chloroplasts that absorbs the light energy needed for photosynthesis
• Plants have less chlorophyll


  They won't be able to carry out as much photosynthesis
• Factors that can reduce chlorophyll in plants


  • Disease (e.g. tobacco mosaic virus)
  • Environmental stress
  • Lack of nutrients (e.g. water)
• Limiting factors for photosynthesis


  • Light
  • Carbon dioxide
  • Temperature
• Graphing factors affecting photosynthesis

  1. Plot light intensity on x-axis

  2. Plot rate of photosynthesis on y-axis

  3. As light intensity increases, rate of photosynthesis increases

  4. Rate plateaus when something else becomes limiting (e.g. carbon dioxide or temperature)
• Graphing carbon dioxide effect on photosynthesis


  1. Rate of photosynthesis increases with carbon dioxide concentration

  2. Plateaus when something else becomes limiting
• Graphing temperature effect on photosynthesis


  1. Rate increases with temperature initially

  2. Rate starts to drop as enzymes denature (around 45°C)
• Everything from here on is higher tier GCSE biology
• Multiple limiting factors shown on one graph


  Comparing curves at different temperatures or carbon dioxide concentrations shows which factor is limiting
• Farmers creating optimal conditions for photosynthesis


  • Greenhouses to trap heat and provide light
  • Artificial lighting
  • Pumping in carbon dioxide
  • Using paraffin heaters
  • Applying fertilizers
  • Using pesticides
• Creating optimal conditions for photosynthesis can be costly for farmers