Chapter 8: Photosynthesis

• Where does photosynthesis occur?

  chloroplasts in the leaves of a plant
• What is the name of the green pigment in the leaves?

  chlorophyll
• What type of reaction is photosynthesis?

  endothermic
• What type of energy is used in photosynthesis?

  light energy
• Give the word equation for photosynthesis.

  carbon dioxide + water ➞ glucose + oxygen
• Give the balanced symbol equation for photosynthesis.

  6CO2 + 6H2O ➞ C6H12O6 + 6O2
• Define the term limiting factor.

  anything that limits the rate of a reaction when it is in short supply
• Give the limiting factors of photosynthesis.

  • temperature

  • carbon dioxide concentration

  • light intensity

  • amount of chlorophyll
• Describe how light intensity affects the rate of photosynthesis.

  increasing light intensity increases the rate of photosynthesis until another factor becomes limiting
• Describe how carbon dioxide concentration affects the rate of photosynthesis.

  increasing carbon dioxide concentration increases the rate of photosynthesis until another factor becomes limiting
• Describe how temperature affects the rate of photosynthesis.

  increasing temperature increases the rate of photosynthesis as the reaction rate increases – at high temperatures enzymes are denatured so the rate of photosynthesis quickly decreases
• Give the equation for the inverse square law for light intensity.

  light intensity ∝ 1 / distance2
• Why are limiting factors important in the economics of growing plants in greenhouses?

  greenhouses need to produce the maximum rate of photosynthesis whilst making profit
• How do plants use the glucose produced in photosynthesis?(5)

  • respiration

  • convert it into insoluble starch for storage

  • produce fat or oil for storage

  • produce cellulose to strengthen cell walls

  • produce amino acids for protein synthesis
• Name the insoluble storage carbohydrate found in potato tubers.

  Starch
• Describe 4 adaptations of a leaf for photosynthesis.

  • Thin & Flat
  • Has veins/ xylem & phloem
  • Has mesophyll cells containing lots of chloroplasts
  • Stomata for gas exchange
• Why do plants require nitrate ions?

  To convert glucose into amino acids/protein for growth
• Explain how tomatoes from tomato growers can reduce the effects of limiting factors in order to obtain larger crops. (5)

  • Grow the tomatoes in a greenhouse or polytunnels
  • Increase the temperature with heaters
  • Use lamps to extend the hours of light
  • Control levels of CO2
  • Use hydroponics to supply nitrate & other essential ions
• What factors do tomato growers need to take into account to maximise profits?

  Cost of electricity:

  • for providing CO2
  • of hydroponic solutions
  • of computer technology to control the conditions of greenhouses/ polytunnels & other equipment, labour
• Give 8 control variables of the photosynthesis practical

  • volume of water
  • temperature of water
  • CO₂ availability
  • mass
  • amount of pondweed
  • light intensity
  • light colour
  • pH
• What mineral ion stops the leaves turning yellow?

  magnesium