• 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