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• Photosynthesis

  A chemical reaction that occurs in the chloroplasts of plants in which the energy in light is stored in glucose
• Glucose


  A sugar produced by plants in photosynthesis and used by all living organisms to release energy during respiration
• Photosynthesis


  • Occurs in chloroplasts found within cells
  • Chloroplasts contain the green pigment chlorophyll which absorbs light
  • The plant uses the glucose to grow and make other useful substances
  • The glucose can also be broken down in the plant by respiration
• Respiration


  A chemical reaction that occurs in the mitochondria of cells in which glucose and oxygen react to produce carbon dioxide and water, releasing energy
• Plants


  • Have adaptations to help them photosynthesise and survive
  • Gases like oxygen and carbon dioxide can travel through tiny holes underneath the leaf called stomata
  • Carbon dioxide diffuses into the cells found within the leaf to help carry out photosynthesis
  • Oxygen is released from these cells as a product of photosynthesis
• Photosynthesis


  Carbon dioxide + water -> glucose + oxygen
• Respiration


  Oxygen + glucose -> water + carbon dioxide
• The reactants and products of photosynthesis and aerobic respiration are opposites
• When plants respire


  • Day (light) - Photosynthesis and respiration occur, carbon dioxide goes in, oxygen and water vapour go out
  • Night (dark) - Only respiration occurs, no gas exchange as stomata close
• Light is one factor that affects the rate of photosynthesis
• Other factors such as the levels of carbon dioxide, presence of chlorophyll, water and temperature can also affect the rate of photosynthesis
• Photosynthesis


  A chemical reaction that occurs in the chloroplasts of plants in which the energy in light is stored in glucose
• Glucose


  A sugar produced by plants in photosynthesis and used by all living organisms to release energy during respiration
• Photosynthesis


  • Occurs in chloroplasts found within cells
  • Chloroplasts contain the green pigment chlorophyll which absorbs light
  • The plant uses the glucose to grow and make other useful substances
  • The glucose can also be broken down in the plant by respiration
• Respiration


  A chemical reaction that occurs in the mitochondria of cells in which glucose and oxygen react to produce carbon dioxide and water, releasing energy
• Plants


  • Have adaptations to help them photosynthesise and survive
  • Gases like oxygen and carbon dioxide can travel through tiny holes underneath the leaf called stomata
  • Carbon dioxide diffuses into the cells found within the leaf to help carry out photosynthesis
  • Oxygen is released from these cells as a product of photosynthesis
• Photosynthesis


  Carbon dioxide + water -> glucose + oxygen
• Respiration


  Oxygen + glucose -> water + carbon dioxide
• The reactants and products of photosynthesis and aerobic respiration are opposites
• When plants respire


  • Day (light) - Photosynthesis and respiration occur, carbon dioxide goes in, oxygen and water vapour go out
  • Night (dark) - Only respiration occurs, no gas exchange as stomata close
• Light is one factor that affects the rate of photosynthesis
• Other factors such as the levels of carbon dioxide, presence of chlorophyll, water and temperature can also affect the rate of photosynthesis
• Factors affecting the rate of photosynthesis in crop growing


  • Light intensity
  • Temperature
  • Carbon dioxide
  • Water supply
  • Chlorophyll
• Limiting factor


  Something that disrupts the growth or abundance of any organisms or population
• Photosynthesis slows down or stops if the conditions aren't sufficient enough
• Photosynthesis


  1. Light shines on leaves

  2. Water and carbon dioxide are available

  3. Reaction quickly slows and then stops if carbon dioxide is removed

  4. No reaction if light and carbon dioxide are present but no water

  5. Rate slows down if temperature falls

  6. Slows down if water and carbon dioxide are reduced

  7. Stops completely at night-time
• Farmers use lights to extend the growing cycle of vegetable plants, making sure we all have enough food to eat all year round
• Main things that affect the rate of photosynthesis


  • Light intensity
  • Carbon dioxide concentration
  • Temperature
  • Water supply
• Farmers control the environment in a greenhouse to increase the rate of photosynthesis by increasing the limiting factors so crops can grow quicker and farmers can produce more in the same space of time
• Crops that do well from the higher rate of photosynthesis


  • Tomatoes
  • Lettuce
• Farmers can add additional carbon dioxide into the greenhouse to increase the concentration, which then increases the rate of photosynthesis of the crops
• Farmers usually use a handheld electronic device to measure the rate of photosynthesis, but you could do this at home using pondweed by counting the bubbles of oxygen being produced
• Grass growth rate in winter

  Slows down because the temperature is low
• Farmers make photosynthesis happen at night


  Use lights to simulate the sun
• At a certain point the addition of more light, heating, carbon dioxide or water will not increase the rate of photosynthesis any further, as a second factor becomes limiting
• Irrigation systems in greenhouses help to increase the production of plants
• Farmers try to get the maximum growth out of crops by manipulating the conditions within their greenhouse, such as trapping the sun's heat, using a paraffin heater, adding fertilisers and pesticides
• To maintain greenhouse temperatures during cooler weather, water is heated to 85°C and circulated throughout greenhouses, with an average hot water tank having a 158,500 gallon capacity, which could supply enough hot water for 7,925 showers
• This is an example of a common experiment used to investigate light intensity and the rate of photosynthesis
• Investigating the rate of photosynthesis

  1. Set up the apparatus

  2. Leave for five minutes for the pondweed to acclimatise to the new light intensity

  3. Count the number of bubbles given off in one minute

  4. Move the light 10 cm further back

  5. Leave for five minutes for the pondweed to acclimatise again

  6. Count the number of bubbles given off in one minute

  7. Repeat by moving the lamp away by 10 cm intervals until 50 cm is reached