Enzymes and Respiration

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Respiration is not 'Breathing In and Out'

Respiration invloves many reactions, many of which are catalysed by enzymes. This is important because respiration releases energy.

Respiration is the process of releasing energy from the breakdown of glucose and it happens in every cell in our body.

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Aerobic Respiration

Aerobi respiration uses oxygen. It's the most effective way of releasing energy from glucose.

It goes on all the time in animals and plants.

Most of the reactions in aerobic respiration happen inside the mitochondria.

Glucose+Oxygen----->Carbon Dioxide+Water+Energy

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Respiration Releases Energy

  • To build large molecules from smaller ones
  • In animals to allow the muscles to contract
  • It is used in mammals and birds to regulate their body temperature
  • In plants, to build sugars, nitrates, and other nutrients into amino acids, which are then built into proteins.
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Exercise Increases the Heart Rate

Muscles are made up of muscle cells, these use oxygen to release energy from glucose, which is then used to contract the muscles.

An increase in muscle activity means that more gluocose and oxygen needs to be supplied to the muscle cells. Extra carbon dioxide needs to be removed from the muscle cells. For this to happen the blood has to flow at a faster rate.

This is why physical activity:

  • Increases your breathing rate and makes you breath more deeply to meet the demand for more oxygen.
  • Increases the speed at which the heart pumps.
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Glycogen Is used during Exercise

Some glucose from food is stored as glycogen.

Glycogen's mainly stored in the liver, but each muscle has its own store.

During vigorous exercise muscles use glucose rapidly, so some of the stored glycogen is converted back into glucose to provide more energy.

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Anaerobic Respiration

When you do vigorous exercise and your body can't cupply enough oxygen to your muscles, they start doing anaerobic respiration instead of aerobic respiration. This means that it is an incomplete breakdown of glucose which produces lactic acid.

Glucose----->Energy+Lactic Acid

This is not the best way to convert glucose to energy because lactic acid builds up in the muscles, which gets painful. It also causes muscle fatigue which means that the muscles stop contracting efficiently as they get tired.

It also doesn't release as much energy as aerobic respiration.

The advantage is that at least you can keep using your muscles for a while longer.

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Anaerobic Respirarion Leads to oxygen Debt

After using anaerobic respiraration and you've finished exercising then you'll have something which is called an 'oxygen debt.' This means that you have to repay the oxygen that you didn't get to your muscles in time because your lungs, heart and blood couldn't keep up with the demand earlier on.

This causes you to brearthe hard for a while after you stop exercising so you can get more oxygen into you blood. Blood flows through your muscles to remove the lactic acid by oxidising it to harmless carbon dioxide and water.

While high levels of carbon dioxide and lactic acid are detected in the blood the pulse and breathing rate remain high to try and rectify the situation.

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