Photosynthesis

2.8.3 Genetic manipulation

3.2 Exchange and transport

Photosynthesis

  1. Mechanism

    1. Light energy is absorbed by chlorophyll, which is found in chloroplasts in some plant cells and algae
    2. This energy is used to convert carbon dioxide from the air and water from the soil into glucose
    3. Oxygen is released as a by-product
    4. Photosynthesis is summarised by the equation: 6CO2 (g) + 6H2O(l) light energy———————→ C6H12O6 (aq) + 6O2 (g)

  2. Rate

    1. Limiting factors

      1. Low temperature, since enzymes do not work optimally
      2. Shortage of carbon dioxide
      3. Shortage of light
      4. Lack of chlorophyll
    2. In a greenhouse: temperature, carbon dioxide concentration and light intensity are enhanced to ensure optimum photosynthesising conditions
    3. However, greenhouses can be costly in terms of building space, electricity for heating & lighting and control systems such as computers, so a cost-benefit analysis must be done to balance higher yields against higher costs

  3. Uses of glucose

    1. Respiration
    2. Converted into insoluble starch for storage
    3. To produce fat or oil for storage
    4. To produce cellulose, which strengthens the cell wall
    5. To produce proteins

  4. Protein production

    1. To produce proteins, plants also use nitrate ions from the soil
    2. Carnivorous plants, such as the Venus Fly Trap, are adapted to live in nutrient-poor soil since they obtain most of their nutrients from the animals they catch, such as insects