B8 - Photosynthesis

• Photosynthesis


  • A chemical reaction in which energy is transferred from the environment as light from the Sun to the leaves of a plant
  • An endothermic reaction
• Chlorophyll


  • the green pigment in chloroplasts in leaves
  • absorbs light energy
• Leaves are well-adapted to increase rates of photosynthesis
• Limiting factor


  Anything that limits the rate of a reaction when it is in short supply
• Limiting factors of photosynthesis


  • temperature
  • carbon dioxide concentration
  • light intensity
  • amount of chlorophyll
• • Less chlorophyll in the leaves reduces the rate of photosynthesis
  • More chlorophyll may be produced by plants in well-lit areas to increase the photosynthesis rate
• carbon dioxide + water -> glucose + oxygen
• Temperature as a limiting factor


  • Low temperatures
  • the rate of photosynthesis is low
  • the reactant molecules have less kinetic energy
  • High temperatures
  • photosynthesis is an enzyme-controlled reaction
  • enzymes denature at high temperatures so the rate decreases
• Carbon dioxide as a limiting factor


  • Higher concentration
  • carbon dioxide is used in photosynthesis, so higher concentration means higher rate
  • At a certain point, another factor becomes limiting
  • Carbon dioxide is often the limiting factor for photosynthesis
• Light intensity as a limiting factor


  • Light energy is needed for photosynthesis
  • increasing light intensity increases the rate of photosynthesis
  • At a certain point, another factor becomes limiting
  • Photosynthesis will stop if there is little or no light
• Greenhouse economics


  • Commercial greenhouses control limiting factors to get the highest rate of photosynthesis possible
  • This is to grow plants as quickly as possible or produce the highest yields while still making profit
• Uses of glucose produced in photosynthesis


  • for respiration to release energy
  • produce cellulose to strengthen cell walls
  • produce amino acids for protein synthesis
  • plants also need nitrate ions from the soil for this
  • produce lipids for storage
  • converted into insoluble starch for storage