B2 2

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…