B8

• Photoynthesis (defenition) 


  a chemical reaction that takes place in the chloroplasts of green plant cells, where light energy is used to convert carbon dioxide and water into glucose and oxygen
• photosynthesis

  • plants make their own food
  • endothermic reaction - needs an input of energy from the environment
• ideal conditions

  greenhosues are used by farmers to grow plants in the perfect conditions
• how does a greenhouse help plants grow?

  • help's trap sun's heat
  • makes sure temperature doesn't become limiting
  • artificial light when sun goes down
  • heater during winter
  • shades and ventilation in summer
  • paraffin heater to increase levels of CO2
  • free from pests/diseases
  • farmers can add fertilisers which helps gain all minerals for plants
  • expensive
• Word equation

  carbon dioxide + water - glucose +oxygen
• chemical equation

  6CO2 + 6H2O - C6H12O6 + 6O2
• light intensity

  • brighter the light the more light energy
  • moe light energy the faster the photosynthesis
  • plants found in areas of lower light don't tend to grow as tall
  • too much light - damage
  • light intensity = 1/distance2
• temperature

  • photoynthesis is controlled by enzymes which works best at warmer temperatures
  • too hot - enzymes denature - photosynthesis stops
• carbon dioxide

  more CO2 - more photosynthesis
• chlorophyll

  • can be affected by diseases (TMV) or environmental stress such as lack of nutrients
  • these factors can cause chloroplats to stop making chlorophyll needed for photosynthesis
• limiting factor

  if one of the factors are restricted - rate of photosynthesis will be below the minimum possible rate
• use of glucose by plants

  • to provide cellulose which strengthens plant cell walls
  • to be converted into insoluble starch for storage inside cells or special areas like roots
  • to be converted into amino acids for protein synthesis - glucose is combined with nitrate ions absorbed from the soil. specific amino acids join in long chains to make a named protein
  • to produce fats or oils for storage. seeds and nuts contain lots of fats and oils as an energy store