Aerobic and Anaerobic Respiration

• Respiration is the chemical reaction that releases energy from glucose in cells.
• Mitochondria are structures in cells where respiration happens. Respiration happens in all cells all the time.
• The energy from respiration is needed for life processes such as movement, growth and chemical reactions (MRS C GREN).
• List the 8 life processes from the acronym MRS C GREN.


  Movement, Reproduction, Sensitivity, Control, Growth, Respiration, Excretion, Nutrition.
• In aerobic respiration, the glucose is completely broken down into carbon dioxide and water. Oxygen is involved in the reaction and lots of energy is released.
• Word equation for aerobic respiration

  Glucose + Oxygen -> Carbon dioxide + Water + Lots of energy (as ATP)
• Chemical equation for aerobic respiration 

  C6H12O6 + 6O2 -> 6CO2 + 6H2O
• How oxygen (reactant) gets in our body: Oxygen is taken into the cell by the process of diffusion.

  Diffusion is the movement of molecules from a region of its higher concentration to a region of its lower concentration.
• How glucose (reactant) gets into our body: Glucose travels from the small intestine into the bloodstream. This is done by diffusion or active transport through the villi of the small intestine into the bloodstream.

  Then, glucose travels in the blood by dissolving in the blood plasma (liquid).

  Lastly, glucose travels from the blood into the body cells. When they reach cells which have a lower concentration of glucose than the blood, the glucose diffuses into the cells.
• Products of respiration:

  (1) Water is mainly used for chemical reactions and transporting substances in the blood. It also plays an important role in controlling body temperature (sweat).

  (2) Carbon dioxide is a toxic waste product so it is removed by exhaling. Carbon dioxide diffuses into the blood plasma and is transported from respiring body cells to the lungs.
• Anaerobic respiration occurs when there is not enough oxygen for aerobic respiration.

  The glucose is only partially broken down and oxygen is not used. Anaerobic respiration allows a little energy to be released from the glucose, but much less than with aerobic respiration.

  However, this process does generate some energy, even when there is a shortage of oxygen.
• Word and chemical equation for anaerobic respiration in animals.

  (1) Glucose -> lactic acid + a little energy (as ATP)

  (2) C6H12O6 -> 2C3H6O3 + a little energy (as ATP)
• Word and chemical equation for anaerobic respiration in plants and fungi.

  (1) Glucose -> alcohol + carbon dioxide + a little energy (as ATP)

  (2) C6H12O6 -> 2C2H5OH + 2CO2 + a little energy (as ATP)
• How lactic acid is broken down (in animals): Oxygen breaks down lactic acid into carbon dioxide and water.
• Why do you continue to breathe heavily for a while after you finish exercising?

  1. Muscles cells need more energy when sprinting/contracting 
  2. This requires more respiration so more oxygen 
  3. Despite an increase in breathing rate, not enough oxygen is delivered to meet the demand of the muscle cells 
  4. So the muscle cells respire anaerobically which produces lactic acid and only a little amount of energy/ATP. 
  5. The lactic acid builds up in the muscles. 
  6. The extra oxygen you inhale after exercise reacts with the lactic acid in your muscles/liver, breaking it down into carbon dioxide and water. 
• Continued: Why do you continue to breathe heavily for a while after you finish exercising?

  (7) The amount of extra oxygen you need to breathe in to break down the lactic acid is known as oxygen debt.
• Anaerobic respiration releases less energy per molecule of glucose than aerobic respiration.
• Advantages of aerobic respiration:

  (1) Aerobic respiration releases more energy per molecule of glucose than anaerobic respiration. 

  (2)Aerobic respiration does not produce an oxygen debt.
• Advantages of anaerobic respiration:

  (1) Anaerobic respiration allows the muscles to continue contracting without oxygen. 

  (2) Quick release of energy.
• Disadvantages of aerobic respiration:

  (1) Aerobic respiration cannot take place during intense exercise when not enough oxygen can be delivered to the muscles. 

  (2) Slower process to release energy.
• Disadvantages of anaerobic respiration:

  (1) Anaerobic respiration produces lactic acid which causes muscle fatigue and cramps. This means anaerobic respiration cannot be used for very long. 

  (2) Anaerobic respiration releases less energy per molecule of glucose than aerobic respiration. 

  (3) An oxygen debt is created from anaerobic respiration so more oxygen must be inhaled following intense exercise to break down the lactic acid.
• Most living organisms benefit from being able to respire both aerobically and anaerobically. This means they can respond to the changing circumstances in which they find themselves. 

  For most organisms, anaerobic respiration is a short-term solution to a temporary shortage of oxygen. However, some organisms (including certain bacteria) can only respire anaerobically and cannot live in the presence of oxygen.
• When an athlete is exercising very hard, the oxygen supply may be insufficient to support aerobic respiration. Despite the best effort of the athlete's lungs and circulation, the supply might not be enough for the work the muscles are doing. In this case, some of the energy for the exercise may be obtained from glucose by anaerobic respiration. The lactic acid formed as a consequence represents the 'oxygen debt. This debt is 'repaid' by the athlete, who continues to breathe hard after the exercise has finished. This allows the lactic acid to be reprocessed to glucose.
• Air spaces in the soil usually allow plant root cells to respire aerobically. However, if the soil becomes flooded, the air spaces become filled with water, so the plant root cells may have to respire anaerobically. If the flooding goes on too long, the alcohol produced can poison the roots, leading to the death of the plant.
• When yeast cells (a fungus) are mixed into dough for making bread, they soon use up all of the oxygen. During the proving stage of bread making, the yeast cells respire the sugars in the dough anaerobically to produce ethanol and carbon dioxide. The trapped carbon dioxide makes the holes in the bread and this helps the bread to rise. The alcohol evaporates off during the baking stage.
• Biotechnology is the use of biological process or organisms to create useful products.
• Word equation for biotechnology.

  Glucose -> Ethanol + Carbon dioxide