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  • Created on: 06-04-14 13:51

Enzymes and Respiration

Respiration is the process of releasing energy from glucose whicih goes on in every cell.. Involves many reactions which are catalysed by enzymes.

Release energy:

  • To build up larger molecules from smaller ones
  • In animlas to allow the muscles
  • Mammals and birds the energy is used to keep their body temperatures  stedy
  • In plants to build sugars, nitrates and other amino acids  which are then built into proteins

Aerobic respiration

  • Uses oxygen
  • Most effiecient way to release energy from glucose
  • All the time in plants and animals
  • Happens inside mitochondria
  • glucose+oxygen=> carbon dioxide+water+energy
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  • Muscles are made of muscle cells.
  • Use oxygen to release energy from glucose, used to contract muscles
  • Increas in muscle activity=> muscle cells need more glucose and oxygen, extra carbon dioxide needs to be removed. Blood has to flow at a faster rate.

This is why physical activity

  • Increses breathing rate, make you breath more deeply to meet demand for extra oxygen
  • Increases the rate at which the heart pumps


  • Glucose from food stored as glycogen
  • Mainly stored in the liver, but each muscle has its own store
  • Vigourous exercise muscles use glucose rapidly so some of the stored glycogen is converted back to glucose to provide more energy
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Anaerobic respiration

  • When doing vigorous exercise body can't supply enough oxygen to your muscles=> anerobic respiration
  • Anaerobic means without oxygen
  • glucose=>energy+latic acid
  • Incomplete breakdown of glucose which produces lactic acid
  • Not best way to convert glucose into energy - lactic acid builds up in the muscles which gets painful.
  • Causes muscle fatigue- the muscles get tired and stop contracting effeciently
  • Doesn't release as much energy as aerobic respiration
  • Advantage=> keep using muscles for a while longer

Oxygen Debt

  • Repay the oxygen that didn't get t muscles in time because lungs, heart and blood couldn't keep up with the demand
  • Breath heavily after stop exercising to get more oxygen into your blood
  • Blood flows through your muscles to remove the latic acid by oxidising it to harmless CO2 and water
  • Pulse and breathing rate stay high while high evels of  CO2 & latic acid are detected in blood
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Use of enzymes

Biological detergents

  • Biolgical ingredients in biological detergents and washing powders
  • Mainly protein- degesting enzymes (proteases) and fat-digesting enzymes (lipases)
  • Enzymes break down animal and plant matter- ideal for removing stains like food or blood
  • More effective at working at low temperatures (30) than other types of detergents

Changing foods

  • Proteins in some baby foods pre-digested using proteases so easier for baby to digest
  • Carbohydrases can turn starch syrup into sugar syrup
  • Glucose syrup can be turned into fructose syrup using an isomerase enzyme Fructose is sweeter so you use less of it- good for slimming foods and drinks
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Advantages and disadvantags of enzymes


  • Specific- only catalyse reaction you want them to
  • Lower temperatures and pressures means a lower cost and saves energy
  • Enzymes work for a long time,
  • Biodegradabe cause less environmental pollution


  • People can develop allergies to the enzymes
  • Denatured even by a small increase in temperature
  • Suceptible to poisons and changes in pH- conditions must be tightly controlled
  • Expensive to produce
  • Contamination of enzyme with other substances can affect the reaction
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