Biology GCSE Enzymes

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  • Enzymes
    • Uses in the home and in industry
      • Industry: protease enzymes are used the pre-digest the protein in some baby foods
      • carbohydrase enzymes are used to convert starch into sugar syrup (for confectionary)
      • Isomerase is used to convert glucose syrup into fructose syrup which is sweeter and can therefore be used in smaller quantities in slimming foods
      • In industry, enzymes are used to bring about reactions at normal temperatures and pressures that would otherwise require expensive, energy-demanding equipment
        • However, most enzymes are denatured at high temperatures and many are costly to produce
          • Enzymes are biological catalysts
    • Bile
      • Produced by the liver
      • Stored in the gall bladder and then carried into the small intestine through the bile duct
      • Enzymes in the stomach work best in acidic conditions, so the stomach produces hydrochloric acid to provide these conditions. Bile neutralises the acid that was added to the food in the stomach and produces alkaline conditions in which enzymes in the small intestine work most effectively
      • Bile emulsifies lipids - breaking large drops of lipids into smaller droplets, which increases the surface area of the lipids so that lipase enzymes can digest the fat more quickly
    • Enzymes are proteins - protein molecules are made up of long chains of amino acids
      • These long chains are folded to produce a specific shape that enables other molecules to fit into the protein (enzyme)
      • Proteins act as structural components of issues such as muscles, hormones, antibodies, catalysts
        • Catalysts are substances which increase the rate of chemical reactions by providing a different reaction pathway for the reactants with a  lower activation energy. They do this without being changed or used up in the reaction process.
          • Enzymes are biological catalysts
    • Proteins have many functions, both inside and outside the cells of living organisms
      • Some enzymes work inside cells (eg, for respiration) and some work outside the body cells (eg, in digestion)
        • The digestive enzymes are produced by specialised cells in glands and in the lining of the gut
          • The enzymes then pass out of the cells into the gut where they come into contact with food molecules. They catalyse the breakdown of large insoluble molecules into smaller soluble molecules so that they can be absorbed and pass into the bloodstream.
            • In industry, enzymes are used to bring about reactions at normal temperatures and pressures that would otherwise require expensive, energy-demanding equipment
              • However, most enzymes are denatured at high temperatures and many are costly to produce
            • The shape of an enzyme is vital for its function. The active site is part of the enzyme that temporarily binds to the substrate. The shape of the active site of an enzyme is specific to a certain substrate
              • High temperatures change the shape of the enzyme's active site.
              • Different enzymes work best at different pH values. An enzyme will not function if the temperature is too high or if the pH is too far from the optimum pH
              • When the shape of the active site is changed irreversibly, the enzyme is said to be denatured
              • Amylase is produced in the salivary glands, the pancreas and small intestine. Amylase works in the mouth and small intestine. Starch into sugars
                • Protease is produced in the stomach, small intestine and pancreas. It works in the stomach and small intestine
                  • Protease catalyses the breakdown of proteins into amino acids. The protease enzymes in the stomach work most effectively in acidic conditions so the stomach produces hydrochloric acid
                  • Lipase breaks down lipids (fats and oils) into fatty acids and glycerol in the small intestine. It is produced by the small intestine and the pancreas

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