B8: photosynthesis

• Photosynthesis


  An endothermic process that requires energy from the external environment (sunlight) in order for the reaction to proceed
• Photosynthesis


  1. Break down bonds in water and carbon dioxide

  2. Reform bonds to make glucose and oxygen
• Leaf


  • Full of air gaps to allow gases to move in and out
  • Contains xylem to transport water
  • Contains palisade mesophyll layer with chloroplasts - site of photosynthesis
  • Contains chlorophyll that absorbs sunlight and converts it to energy
• Leaf surface area


  Larger surface area means more sunlight can hit the leaf, enabling more photosynthesis
• Use of glucose in plants

  1. Respiration

  2. Conversion to cellulose to strengthen cell walls

  3. Storage as starch

  4. Conversion to amino acids for enzymes and proteins

  5. Conversion to lipids for energy storage
• Limiting factors for photosynthesis

  • Light intensity
  • Temperature
  • Carbon dioxide concentration
• As light intensity increases

  Rate of photosynthesis increases until other limiting factors take effect
• As temperature increases


  Rate of photosynthesis increases until enzymes become denatured at too high a temperature
• As carbon dioxide concentration increases

  Rate of photosynthesis increases until other limiting factors take effect
• Greenhouses control light, temperature and carbon dioxide to maximise photosynthesis and plant growth
• Greenhouses also control water intake through hydroponics to provide optimal nutrient supply