topic 4

Cards (15)

  • 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
  • Showing that a plant gives off oxygen during photosynthesis
    Using a water plant (eg. Elodea), collect gas bubbles produced during photosynthesis. The gas will relight a glowing splint as it contains oxygen.
  • 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
  • Inverse square law

    Light intensity1 / distance^2
  • Uses of glucose produced during photosynthesis
    • Respiration
    • Starch for storage
    • Cellulose for strength
    • Amino acid and protein synthesis (combined with nitrates)
    • Lipids for energy storage in seeds