Photosynthesis

• EQUATION

  • (light energy) carbon dioxide + water > oxygen + glucose
• EXPLAIN

  • carbon dioxide, water is used by plant
  • carbon dioxide is from the atmosphere, water from the soil
  • light energy absorbed by chlorophyll
  • plant produces glucose and oxygen
  • the oxygen is used for respiration, excess released through stomata by gas exchange
• Uses of glucose

  • animals store glucose as glycogen (and some fat)
  • plants store glucose as starch
• Palisade mesophyll layer has many chloroplasts and a large surface area, so maximum amount of light can be absorbed for photosynthesis.
• Guard cells surround stomata allowing carbon dioxide to enter and oxygen to exit.
• Upper epidermis is transparent, allowing light to reach the palisade layers.
• Spongy layer has large air spaces to allow gas exchange
• Limiting factors

  • depending on what's in short supply, only one limiting factor can act at a time
  • things that affect the rate of photosynthesis are limiting factors
  • eg light, temperature
• HOW DOES CO2 AFFECT THE RATE OF PHOTOSYNTHESIS?

  • concentration of carbon dioxide increasing increases the rate of photosynthesis
  • until a certain point where the rate levels off
  • carbon dioxide levels are still increasing so it must be another factor limiting the rate
• HOW DOES LIGHT INTENSITY AFFECT THE RATE OF PHOTOSYNTHESIS?

  • as it increases so does the rate of photosynthesis
  • until a certain point where rate levels off
  • light intensity is still increasing so a LIMITING FACTOR must be there (temperature or CO2 concentration)
• HOW DOES TEMPERATURE AFFECT RATE OF PHOTOSYNTHESIS?

  • as temperature increases so does rate of photosynthesis
  • until it reaches optimum temperature range where rate is fastest
  • when temperature goes beyond this range, rate of photosynthesis decreases as enzymes denature