Photosynthesis

• Photosynthesis

  The process by which plants synthesise glucose using light energy from the Sun. Light energy is converted into chemical energy.
• Photosynthesis

  Carbon dioxide + water → glucose + oxygen
• Photosynthesis

  An endothermic reaction - energy is transferred from the environment to chloroplasts by light
• Leaf adaptations that maximise the rate of photosynthesis

  • Broad leaves - maximise surface area
  • Thin leaves - short diffusion distance
  • Chlorophyll present - trap light energy
  • Veins - transport water to leaves via xylem, remove photosynthesis products via phloem
  • Air spaces - allow CO2 to enter and O2 to leave
  • Guard cells - control opening of stomata for gaseous exchange and prevent water loss
• Factors that affect the rate of photosynthesis

  • Temperature
  • Light intensity
  • Carbon dioxide concentration
  • Amount of chlorophyll
• Increasing temperature

  Increases the rate of photosynthesis as the kinetic energy of particles is increased. The rate decreases past a certain temperature as enzymes become denatured.
• Increasing light intensity

  Increases the rate of photosynthesis until another factor becomes limiting
• Increasing carbon dioxide concentration

  Increases the rate of photosynthesis (until another factor becomes limiting) as CO2 is required to make glucose
• Decreasing the amount of chlorophyll

  Decreases the rate of photosynthesis as chlorophyll is required to absorb light energy
• Limiting factor

  An environmental factor which can restrict the rate of photosynthesis eg. light intensity
• Calculating the rate of photosynthesis by measuring oxygen production

  Set up bubble potometer apparatus (pondweed in a sealed tube of water, attached to a capillary tube and a gas syringe). Oxygen gas produced causes the bubble in the capillary tube to move. The distance moved by the bubble is used to calculate the volume of oxygen produced.
• Farmers controlling limiting factors

  They can control temperature, light intensity and CO2 concentration to achieve the fastest possible rate of photosynthesis, leading to a greater yield
• Uses of glucose produced during photosynthesis

  • Respiration
  • Amino Acid (combined with nitrate ions) production
  • Cellulose production
  • Store in starch (combined with nitrates)
  • Make oils and fats
• Explain how farmers manipulate the environment for their crops

  Add artificial lights to plants so they can photosynthesise during the night

  Increase the level of CO2 using paraffin heater

  Add heater to make the enzymes work faster
• As the distance of the light from the plant increases, the light intensity decreases - this is an inverse relationship