Respiration gives organisms the energy used to survive.
Aerobic respiration is the breaking down of glucose using oxygen. The equation is:
glucose + oxygen --> carbon dioxide + water + energy
This usually takes place in mitochondria. More mitochondria is found in cells and tissues that need to respirate more, like muscles.
In animals, glucose comes from the foods that we eat, in plants, glucose comes from photosynthesis.
The energy is used for movement growth the breaking down of substances in chemical reactions building larger molecules from smaller ones.
Animals make proteins, fats and carbohydrates + build new tissues, plants make amino acids from sugars and large nutrients from smaller ones, they also comine amino acids to make proteins
Changes During Exercise
Your muscles use energy from respiration for exercise, so when you exercise more the rate of respiration increases.
Glucose is moved from the blood during exercise and if the glucose runs out, stores of glycogen in muscle and liver cells are converted to glucose.
Respiration takes oxygen and produces carbon dioxide which is transported in the blood.
To supply oxygen and remove carbon dioxide, the blood needs to circulate faster, therefore the heart rate will also need to increase.
To take in oxygen and release carbon dioxide your breathing rate will also need to increase as well.
If you exercise more frequently, your body becomes fitter and more able to provide blood supply that muscles need.
If you exercise for a long time your muscles start to fatigue meaning they don't contract as strong as they normally do and don't do as much work and you would feel weak.
This happens because you start to run out of oxygen. Without oxygen you cannot respirate anaerobically so instead your cells perform anaerobic respiration which is where you break downn glucose without using oxygen.
The equation for anaerobic respiration is:
glucose --> lactic acid + energy
Anaerobic produces a lot less energy than aerobic respiration becuae the glucose is only partly broken down however is a lot faster.
After exercise we breathe deeply even though our muscles no longer need to work as vigerously. This is because of oxygen debt.
This is when anaerobic respiration has occoured during exeercise and the lactic acid needs to be removed and recycled. It is moved to the liver where it is oxidised back to glucose.