Chapter 8

• Photosynthesis


  An endothermic process that requires energy from the external environment
• 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, the 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
• Factors affecting rate of photosynthesis

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


  Rate of photosynthesis increases until limited by other factors
• Temperature increases


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


  Rate of photosynthesis increases until limited by other factors
• Units for measuring factors affecting photosynthesis rate: light intensity in lumens, temperature in degrees Celsius, carbon dioxide concentration in percentages
• 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