Energy from Respiration

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  • Created by: Hope
  • Created on: 17-04-14 17:35

Aerobic Respiration

Respiration releases energy for cells from glucose. This can be aerobic respiration, which needs oxygen, or anaerobic respiration, which does not. During exercise, the breathing rate and heart rate increase. During hard exercise an oxygen debt may build up.

Aerobic respiration is using oxygen 

glucose + oxygen → carbon dioxide + water (+ energy)

Glucose and oxyen are used up and carbon dioxide and water are produced as waste products. Aerobic respiration happens inside all animals and plants usually inside mitochondria. All of the reactions are controlled by enzymes. 

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Using Energy and Exercise

Energy released by the respiration is used by the organism in many ways...

  • Build larger molecules from smaller ones (e.g. amino acids being built up into protiens)
  • In animals, to enable muscles to contract
  • In mammals and birdsm to maintain a steady body temperature in colder surroundings
  • Breaking larger molecules into smaller ones.


During exercise the muscles respire more quickly than they do at rest this means...

  • Oxygen and glucose must be delivered to muscles more quickly 
  • Waste carbon dioxide must be carried away from the muscles quicker 
  • This can be achieved by increasing the heart rate, the rate of breathing and the depth of breathing - The increased rate and depth of breathing increases the rate of gaseous exchange

Muscles store glucose as glycogen which can be converted back to glycose for use during exercise.

(remember humans store gluocose as glycogen and animals store glucose as starch)

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Anaerobic Respiration

Not enough oxygen may reach the muscles during exercise. When this happens, they use anaerobic respiration to obtain energy.

Anaerobic respiration involves the incomplete breakdown of glucose. It releases around 5% of the energy released by aerobic respiration, per molecule of glucose. The waste product is lactic acid rather than carbon dioxide and water:

glucose → lactic acid (+ little energy)

Exercising for long periods of time can often make you feel fatigued this is because of the build up of lactic acid because of the anaerobic respiration. The lactic acid is removed by blood flowing through them.

Oxygen Debt 

In anaerobic the breakdown of glucose is incomplete

The amount of oxygen needed to oxidise lactic acid to carbon dioxide and water.

The exsistence of an oxygen debt explains why we continue to breath deeply after exercise.

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