Topic 4 – Bioenergetics

• Photosynthesis


  6CO2 + 6H2O C6H12O6 + 6O2
• Uses of glucose


  • Energy - respiration
  • Cellulose cell walls
  • Combine with nitrates to form amino acids and then proteins
  • Turns into lipids (fats) in seeds
  • Starch - stored for winter
• Limiting factor


  Stops reaction from going any faster
• Limiting factors in Photosynthesis

  • Light
  • CO2
  • Temperature
  • Chlorophyll
• The factor on the x-axis is never limiting
• Bringing the light closer

  More O2 will be made as more photosynthesis takes place
• Changing light intensity


  1. Move from 5cm to 15cm (d=3) = makes light (1/32)= x 1/9 times Intensity

  2. Move 50cm to 10cm (d=0.2)= makes light (1/0.2^2)= x 25 times Intensity
• Changing experiment conditions


  1. Effect of temperature - use water bath (keep light constant)

  2. Effect of CO2 - use NaHCO3 to release CO2 (keep light and temp constant)
• Steps to measure effect of light intensity on rate of photosynthesis

  • Light source - specific distances
  • Bubbles of O2
  • Measure volume of O2 from syringe
  • Use a light shield - prevent temperature
  • Repeat experiment - mean vol O2
• Light Intensity


  Inversely proportional to the square of the distance (1/d^2)
• Artificially create the optimum conditions for plant growth
• Conditions to optimise plant growth in a greenhouse

  • Temperature - Sun (day) or heaters (night)
  • Light - Clear windows sunlight (day) or Light bulbs (night)
  • CO2 - Paraffin heater released CO2 if needed
  • Fertilisers - keep the soil nutrient rich for plants to use
  • Walls of greenhouse protect from pests (mice) or harsh weather
• Disadvantages of a greenhouse

  • Expensive to maintain - COSTS!
• Respiration


  Releasing energy from food (glucose) - It is NOT breathing air (ventilation)
• Uses of energy from respiration

  • Build molecules small to large
  • Allow muscles to contract
  • Maintain body temperature
• Metabolism


  All the chemical reactions that take place in your body
• Types of metabolism


  • Building up - e.g. making proteins (Anabolism)
  • Breaking down - e.g. glucose respiration (Catabolism)
• Types of respiration


  • Aerobic - with O2
  • Anaerobic - without O2
• Aerobic respiration

  Glucose + O2 CO2 + H2O
• Anaerobic respiration in animals

  Glucose Lactic acid
• Anaerobic respiration in plants/yeast

  Glucose Ethanol + CO2
• Aerobic respiration


  Releases more energy
• Anaerobic respiration


  Less energy
• Anaerobic respiration


  Get to use muscle for a bit longer
• Body needs more energy


  • Breathing rate increases = Breath in more O2 and remove CO2
  • Heart rate increases = get oxygenated blood around the body
  • Anaerobic respiration = lactic acid
• Oxygen debt


  1. Glucose burned without O2 = Lactic acid

  2. Continue breathing after exercise to remove lactic acid = H2O + CO2

  3. Lactic acid converted back to glucose in the liver