Bioenergetics

• Photosynthesis

  1. Carbon dioxide + water

  2. Glucose + oxygen
• Chlorophyll


  The green pigment found in the chloroplast (organelle)
• Photosynthesis is an endothermic reaction
• Plants carry out photosynthesis only when it's light
• Plants carry out respiration all the time (with or without light)
• Uses of glucose produced in photosynthesis

  • Used for respiration
  • Converted into insoluble starch (storage)
  • Used to produce fat/oil (storage)
  • Used to produce cellulose (strengthen)
  • Used to produce amino acids (produce protein)
• Testing leaves for starch


  1. Put leaf in hot water for 1 minute

  2. Place leaf in boiling tube with ethanol and put that in a water bath for 10 minutes

  3. Remove leaf and place in hot water again

  4. Remove leaf, used tweezers to spread it out on a petri dish and put a few drops of iodine solution on it
• Hot water


  Stops anymore photosynthesis & remove waxy cuticle (iodine can enter cells later)
• Ethanol


  Removes chlorophyll, so that the change in colour can be seen
• Ethanol is flammable, can't be exposed to naked flame
• Hot water (again)


  Rehydrate & soften the leaf
• Limiting factors of photosynthesis

  • Light intensity
  • Carbon dioxide
  • Temperature
  • Amount of chlorophyll
• As light intensity increases

  The rate of photosynthesis increases, until another factor (temperature / CO2) is in short supply
• As CO2 increases


  The rate of photosynthesis increases, until another factor (light intensity / temperature) is in short supply
• As temperature increases


  The rate of photosynthesis increases, until it gets to an optimum, where the photosynthesis peaks
• 0.04% CO2 is a limiting factor for photosynthesis (regardless of temperature)
• 15°C is a limiting factor for photosynthesis
• Inverse square law

  The intensity of light is inversely proportional to the square of the distance from the source
• Gas exchange in the respiratory system

  Oxygen needs to diffuse into the blood stream and carbon dioxide needs to diffuse out
• Adaptations of the lungs

  • Millions of alveoli
  • The alveoli wall is very thin
  • Large blood supply/gas supply
• Emphysema


  Causes shortness of breath, difficulty exercising due to deformed alveoli - reduced surface area for diffusion
• Respiration


  The process of releasing energy from the breakdown of glucose, which goes on in every cell and every living organism
• Aerobic respiration


  1. Glucose + Oxygen

  2. Carbon Dioxide + Water (+ Energy)
• How energy is used by organisms

  • Growth and repair of cells
  • Muscle contraction (movement)
  • To build larger molecules from smaller ones (proteins from amino acids)
  • In mammals and birds, to control body temperature
• Anaerobic respiration


  1. Glucose

  2. Lactic acid
• Anaerobic respiration


  The release of energy from glucose without using oxygen
• Fermentation


  1. Glucose

  2. Ethanol + Carbon Dioxide
• During exercise

  • Breathing rate increases
  • Heart rate increases
• Fitness


  A person's ability to respond to increased energy demand during exercise due to more efficient lungs and heart
• Fitter person's heart rate

  • Lower at rest
  • Increases more slowly during exercise
  • Highest value is lower than unfit person
  • Returns to resting rate faster
• 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
• Conversion of lactic acid


  1. Lactic acid + oxygen

  2. Carbon dioxide + water
• Metabolism


  The sum of all the reactions in a cell or the body
• Examples of metabolism


  • Conversion of glucose to cellulose in plants
  • Conversion of glucose into glycogen in animals and starch in plants for storage
  • Formation of lipid molecules from glycerol and fatty acids
  • Use of glucose and nitrate ions to form amino acids for protein synthesis
  • Breakdown of excess proteins to form urea for excretion
• What is the purpose of the required practical described?

  To investigate light intensity's effect on photosynthesis
• What aquatic organism is suggested for the experiment?

  Pondweed
• What is the sample method for the experiment?

  1. Place pondweed in a beaker.
  2. Shine a light at it from a specific distance.
  3. Record bubbles produced in one minute.
  4. Repeat with different lamp distances.
• What is the independent variable in the experiment?

  Light intensity (distance from the light)
• What is the dependent variable in the experiment?

  Number of bubbles in one minute
• What are the control variables in the experiment?

  • Piece of pondweed
  • Temperature
  • Concentration of carbon dioxide