Bioenergetics

• Photosynthesis


  The process by which plants make glucose from sunlight
• Endothermic reaction


  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. Control variables except independent variable
• 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
• Light intensity


  Inversely proportional to the square of the distance (inverse square law)
• 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
• Exothermic

  Energy is transferred to the environment
• Types of respiration

  • Aerobic (with oxygen)
  • Anaerobic (without oxygen)
• 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 formation from protein breakdown
• Photosynthesis


  The process in which light is used by plants to convert carbon dioxide and water into glucose and oxygen
• Leaves


  • Contain chloroplasts with chlorophyll that can trap light energy for photosynthesis
  • Have a large surface area to absorb light and gases
  • Have stomata for gas exchange
• Endothermic reaction


  A reaction that takes in energy (like photosynthesis)
• Factors affecting rate of photosynthesis

  • Light intensity
  • Carbon dioxide concentration
  • Temperature
  • pH
• As light intensity increases

  Rate of photosynthesis increases up to a point, then levels off
• As carbon dioxide concentration increases

  Rate of photosynthesis increases up to a point, then levels off
• As temperature increases


  Rate of photosynthesis increases up to an optimum, then decreases
• Optimum temperature


  The temperature at which the rate of photosynthesis is maximised
• Enzyme denaturation


  High temperatures cause enzymes to change shape, making them non-functional
• Limiting factor


  The factor present in the least amount that affects the rate of photosynthesis
• Measuring rate of photosynthesis

  1. Use a plant like hydrilla in water, measure oxygen bubbles produced

  2. Vary factors like light, temperature, and measure changes in bubble production
• Uses of glucose produced in photosynthesis

  • Fuel for plant respiration
  • Stored as starch
  • Converted to cellulose for cell walls
  • Converted to proteins and lipids
• Starch


  An insoluble carbohydrate that can store large amounts of glucose without disrupting osmotic balance
• Starch test


  Cover part of a leaf, expose to light, then test with iodine solution - blue-black colour indicates presence of starch
• Greenhouse


  A controlled environment that optimises factors like temperature, light, and carbon dioxide to maximise photosynthesis
• Respiration


  The process of breaking down food to release energy, can be aerobic (with oxygen) or anaerobic (without oxygen)
• Aerobic respiration


  Respiration that occurs in the presence of oxygen, releases more energy than anaerobic respiration
• Anaerobic respiration


  Respiration that occurs in the absence of oxygen, releases less energy than aerobic respiration
• Aerobic respiration


  Respiration that takes place in the presence of oxygen
• Anaerobic respiration


  Respiration that takes place in the absence of oxygen
• Aerobic respiration


  1. Glucose + Oxygen -> Carbon dioxide + Water

  2. Releases more energy
• Anaerobic respiration in plants

  Glucose -> Ethanol + Carbon dioxide
• Anaerobic respiration in animals

  Glucose -> Lactic acid