GCSE B2 Chapter 3

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  • Created by: emma998
  • Created on: 19-03-14 16:41

Proteins catalysts and enzymes

  • Proteins are made up of long chains of amino acids which are folded to produce different shapes
  • The structure of a protein is dependent upon function
  • Proteins can beStructural comonentsHormonesAnti-bodiesCatalysts
  • Enzymes = biological catalysts - they are produced in all living cells and speed up reactions without being used up in them
  • They are large proteins 
  • Their shape is vital for thier function
  • They have an active site which the substrate fits into
  • They can:
    • build large molecules from small ones - starch from glucose
    • Break down large molecules into small ones - digestive enzymes
    • Convert one type of molecule into another - glucose into frustose
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Factors affecting enzyme action


  •  Increasing temperature increases rate of reaction because particles have more energy so move around more, colliding with paticles more frequently and with more energy
  • However a too high temperaure (depends on the enzyme) will cause the active site to change shape meaning the substrate can no longer fit into it so enzymes has denatured


  • Enzymes have a pH which they work best in
  • If the conditions are to alkaline or acidic for an enzyme the active site will change shape and become denatured
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Enzymes in digestion

Some enzymes work outside body cells. Digestive enzymes produced in glands and lining of gut. Pass out of cells and come into contact with food

Amylase enzymes (a carbohydrase)

  • Produced in the salivary glands, pancreas and small intestine
  • Catalyses digestion of starch into simple sugars
  • Digestion occurs in mouth and small intestine

Protease enzymes

  • Produced in stomach, pancreas and small intestine
  • Catalyses digestion of protein into amino acids
  • Digestion occurs in stomach and small intestine

Lipase enzymes

  • Produced in pancreas and small intestine
  • Catalyses digestion of lipids into fatty acids and glycerol
  • Digestion occurs in small intestine
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Speeding up digestion

  • Bile aids the process of digestion
  • Produced in liver
  • Stored in gall bladder
  • Alkaline
  • Bile is squirted onto food molecules as it passes from the stomach to the small intestine neutralising stomach acid on the molecules of food. 
  • This means that conditions in the small intestine are slightly alkaline enabling amylase and lipase enzymes to work at their best
  • Bile also emulsifies fat - breaks into smaller pieces increasing surface area making it quicker for lipase to digest
  • Protease enzymes work best in the stomach where conditions are strongly acidic because glands in the wall of the stomach produce hydrochloric acid
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Making use of enzymes

  • Can bring about reactions at normal temperatures and pressures reducing energy and therefore reducing costs
  • Protease enzymes can be used to pre-digest some baby foods
  • Biological detergents contain protease and lipase enzymes which can remove tough stains by digesting them
  • Isomerase can be used to convert glucose into fructose which is much sweeter so less of it is needed meaning it is much less fattening so can be used in slimming foods
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High-tech enzymes


  • Enzymes are very effective at removing tough stains such as blood, grass and gravy
  • They can be used to bring about reactions at normal temperatures and pressures
  • They can be used to diagnose, control and even cure diseases
  • Enzymes can be re-used so can reduce the cost of equipment


  • Industrial enzymes can be costly to produce
  • They do not work at the higher temperatures needed to kill pathogens
  • Protease enzymes digest some fabrics such as wool
  • They can enter the waterways via the sewage system
  • Allergic reactions can be caused by misusing biological washing powders
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