Bioenergetics

• Photosynthesis


  The process by which plants make glucose from sunlight
• Photosynthesis is an endothermic reaction in which energy is transferred from the environment to the chloroplasts by light
• Photosynthesis


  Carbon dioxide + water → glucose + oxygen
• Factors affecting rate of photosynthesis

  • Temperature
  • Light intensity
  • Carbon dioxide concentration
  • Amount of chlorophyll
• Measuring oxygen production to calculate rate of photosynthesis


  1. Pondweed in test tube

  2. Capillary tube and syringe

  3. Lamp at measured distance

  4. Measure distance bubble moves to calculate oxygen volume

  5. Change variables like temperature, time, light intensity
• Limiting factor


  An environmental condition (such as light intensity) which, in low levels, restricts any increase in the rate of photosynthesis
• Graphs showing limiting factors

  • One line levelling off showing one limiting factor
  • Two lines showing two limiting factors
  • Three lines showing three limiting factors
• Farmers can use knowledge of limiting factors to enhance greenhouse conditions for greater rate of photosynthesis
• Inverse proportion


  Relationship where one factor increases as another decreases
• Inverse square law


  Light intensity is inversely proportional to the square of the distance
• Uses of glucose from photosynthesis

  • For respiration
  • Converted into insoluble starch for storage
  • To produce fat or oil for storage
  • To produce cellulose to strengthen cell walls
  • Combined with nitrates to form amino acids which produce proteins
• Respiration


  The process of transferring energy from glucose so living processes can occur
• Respiration is exothermic as energy is transferred to the environment
• Types of respiration


  • Aerobic (with oxygen)
  • Anaerobic (without oxygen)
• Aerobic respiration


  Glucose + oxygen → carbon dioxide + water
• Anaerobic respiration in animals

  Glucose → lactic acid
• Anaerobic respiration in plants and yeast

  Glucose → ethanol + carbon dioxide
• Oxygen debt


  The amount of extra oxygen the body needs after exercise to react with the accumulated lactic acid and remove it from the cells
• Metabolism


  The sum of all the reactions in a cell or the body, controlled by enzymes
• Metabolic reactions


  • Glucose to starch, glycogen and cellulose
  • Glycerol and fatty acids to lipids
  • Glucose and nitrates to amino acids and proteins
  • Respiration reactions
  • Urea forming from protein breakdown