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  • Respiration is the chemical reaction that breaks down nutrient molecules in living cells to release energy
  • In humans, our cells need energy (ATP) for:
    • muscle contraction
    • making protein molecules: linking together amino acids into longs chains
    • cell division: to repair damaged tissues and so that we can grow
    • active transport
    • transmitting nerve impulses
    • maintenance of constant body temperature
  • Respiration involves the action of enzymes in cells
  • There are two kinds of respiration; aerobic, and anaerobic
    • The main difference between them is that aerobic respiration involves oxygen and anaerobic respiration does not
Aerobic Respiration
  • Aerobic respiration is the chemical reaction in cells that use oxygen to break down nutrient molecules to release energy
  • C6H12O6 → 6CO2 + 6H2O
    Glucose + Oxygen → Carbon-dioxide + Water

Investigation of the Uptake of Oxygen by Respiring Organisms, such as Arthropods, and Germinating Seeds

  • Apparatus Needed:
    • Capillary tube
    • Beaker/container
    • Ruler
    • Rubber stoppers
  • Soda lime contains chemicals that absorb carbon-dioxide
  • It’s important to not let any animals touch the soda lime as it could harm them
  • As the seeds respire, they will produce carbon-dioxide which is absorbed by soda lime
  • The volume of air in the container decreases as oxygen is used up
  • Consequently, the colored water in the 1 ml pipette rises
  • After adjusting the pressure changes in the volume of air in the flask, the rate of oxygen can be measured
  • Experiment:
    • Set up both apparatus as shown in the diagrams.
      • You can use any small organism or germinating seeds in apparatus B.
      • Make sure that the connections between the capillary tubes, rubber stoppers, and containers are completely right
    • Dip the end of the capillary tube of each set of apparatus into oil
      • You should find that a small drop of oil goes into the capillary tube
    • Record the initial position of the oil drop in the apparatus
      • Then continue to record this at regular intervals until you feel that you have enough readings
    • Plot a line graph of your results for both sets of apparatus. Draw both lines in one set of axes
Anaerobic Respiration
  • Anaerobic respiration is the chemical reaction in cells that break down nutrient molecules to release energy without using oxygen
  • Equation for anaerobic respiration in muscles during vigorous exercise :
    • Glucose → lactic acid
  • Lactic acid builds up in muscles and blood during vigorous exercise causing an oxygen debt

How the Oxygen Debt is Removed during Recovery

  • Aerobic respiration of lactic acid in the liver
  • Continuation, after exercise, of fast heart rate to transport lactic acid in blood from muscles to the liver
  • Continuation, after exercise, of deeper breathing supplying oxygen for aerobic respiration of lactic acid
  • Equation for Anaerobic Respiration in Yeast:
    • Glucose → Alcohol + Carbon-dioxide
      C6H12O6 → 2C2H5OH + 2CO2
  • Anaerobic respiration releases much less energy per glucose molecule than aerobic respiration
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