Aerobic respiration takes place constantly in plants and animals.
The process uses glucose and oxygen to release energy.
Carbon dioxide and water are produced as waste products.
Most of the chemical reactions of aerobic respiration take place in the mitochondria and are controlled by enzymes.
The equation of aerobic respiration is:
Glucose + oxygen →Carbon dioxide + water
The energy released May be used by the organism to:
Build a larger molecules from smaller ones
Enable muscle contractions in animals
Maintain a constant body temperature in colder surroundings in mammals and birds
Build sugars nitrates and other nutrients into amino acids and then proteins in plants
The effect of exercise on the body
When you exercise your muscles need more energy so that they can contract
You need to increase the rate at which oxygen and glucose reach the muscle cells for aerobic respiration you also need to remove the extra waste carbon dioxide produced more quickly
The heart rats increases and blood vessels supplying the muscle dilate (widen). This allows more blood containing oxygen and glucose to reach the muscles
Your breathing rate and the depth of each breath also increases. This allows a greater uptake of oxygen and release of carbon dioxide at the lungs
Muscles store glucose as glycogen. The glycogen can be converted back to glucose for use during exercise.
During exercise the heart rate and breathing rate increases to supply the muscles with glucose and oxygen and to remove the extra carbon dioxide produced.
If you use muscles over a long period of time they will get fatigued and stop contracting efficiently. For example this might happen when you lift weights repeatedly for a few minutes or go jogging.
When your muscles cannot get enough oxygen for aerobic respiration they start to respire anaerobically.
The glucose is not completely broken down in anaerobic respiration and lactic acid is produced.
Less energy is released from the glucose in anaerobic respiration
One cause of muscle fatigue is the build up of lactic acid
Blood flowing through muscles removes the lactic acid
What is produced during anaerobic respiration?
Anaerobic respiration is inefficient because the breakdown of glucose is not complete. Instead of carbon dioxide and water lactic acid is produced as a waste product.
Lactic acid causes muscle fatigue. When the exercise has finished this lactic acid must be completely broken down. You still need to take in a lot of oxygen to do this. This extra oxygen needed is known as the oxygen debt. Eventually the oxygen oxidises lactic acid into carbon dioxide and water.
Key points for aerobic respiration:
Aerobic respiration is the release of energy from food when oxygen is available
Most of the reactions for aerobic respiration take place in the mitochondria
Key points for the effect of exercise on the body:
During exercise muscles need more energy
More glucose and oxygen need to be transported to the muscles
To do this there are changes in heart rate in breathing and in blood supply to the actively respiring muscle cells.
Key points for anaerobic respiration:
When muscles work hard for a long time they may have too little oxygen and become fatigued
Muscles use anaerobic respiration if they are short of oxygen
When muscles respire anaerobically they build up an oxygen debt.