B2 2

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  • Created by: Florence
  • Created on: 31-12-12 13:38

B2 2.1

  • Photosynthesis word equation - 
    • Carbon dioxide + water -(light energy)-> glucose + oxygen
  • Glucose is a large molecule and contains energy in its bonds that can be used for growth.
  • Chlorophyll (found in chloroplasts) absorbs light energy, which is used to convert carbon dioxide and water into glucose.
  • Green and white leaves are called variagated leaves - only the green parts contain chlorophyll.
  • Green algae contains chloroplasts and can photosynthesise.
  • To test if a plant is photosynthesising is to test it for starch - Excess sugar produced during photosynthesis is stored as insoluble starch and will show as blue-black.
    • Before iodine is added to leaves they are plunged into boiling and decolourised by heating in ethanol.
  • You can check that oxygen is produced in photosynthesis by collecting and testing it it with a glowing splint.

B2 2.2

  • The rate of photosynthesis is affected by - 
    • temperature
    • light intensity
    • carbon dioxide availability
    • water availability
  • It is limited by
    • low temperature
    • shortage of carbon dioxide
    • shortage of light
  • You can increase an individual limiting factor but the rate of photosynthesis will always be limited by another limiting factor.
  • Increasing the temperature of plants beyond the optimum causes the enzymes that cause photosynthesis to denature, which stops photosynthesis.
  • Light intensity and level of carbon dioxide interact to affect the rate of photosynthesis.
    • They change throughout the day so any one of them may be the limiting factor.
  • Carbon dioxide can be a limiting factor when plants grow densely together as forests or crops.

B2 2.3

  • Stored carbohydrates in plants such as potato or corn helps the plants to survive over the winter and supports new growth in the spring.
  • Some…


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