Biology 3.3 - Photosynthesis

• What is the first stage of photosynthesis called?

  The light reactions
• What happens in the light reactions?

  • The light energy from the sun is trapped by chlorophyll in the chloroplasts and is converted into chemical energy used to generate ATP and h20
  • H2O is split to produce hydrogen and oxygen
  • Oxygen then diffuses from the cell
• What is the second stage of photosynthesis called?

  Carbon fixation
• What happens during Carbon Fixation?

  - A series of enzyme reactions, which use hydrogen and ATP carried from the light reactions with CO2 to produce sugar (glucose)
• What then happens to the sugar generated by photosynthesis?

  - Some glucose is immediately used for respiration- It can be converted into other substances like starch (storage) and cellulose (structural) - Some glucose is converted into fats (using soil nutrients) and amino acids.
• What limits the rate of photosynthesis and plant growth?

  Whatever is in least supply Limiting factors include: CO2 concentration, light intensity and temperature
• Equation for photosynthesis

  Carbon dioxide + water ————- Chlorophyll + light energy > glucose + oxygen
• In what ways could you measure the rate of photosynthesis?

  • Oxygen produced
  • CO2 uptake
  • Glucose/starch production
• In what ways could you test for the products of photosynthesis?

  Add starch - iodine turns from brown to dark blue

  Add glucose - Benedict’s test turns glucose blue to brick red

  Add oxygen - relights a glowing splint
• What is photosynthesis?

  A series of enzyme controlled reaction which allow green plants to make their own food.