Enzymes

Enzymes

1. Proteins, Catalysts & Enzymes

   • Protein molecules are made of long chains of amino acids
   • The long chains are folded to produce specific shapes
   • The shape of a protein depends on its function
   • Proteins can be...
     • structural components of tissue, such as muscle
     • hormones
     • antibodies
     • catalysts
   • Chemical reactions in cells are controlled by proteins called enzymes
   • Enzymes are biological catalysts - they speed up reactions
   • Enzymes are large proteins, and the shape of the enzyme is vital for its function
     • This shape has ab area where other molecules can fit - ACTIVE SITE
   • The substrate in a reaction can be held in the active site and either be connected to another molecule or be broken down
   • Enzymes can...
     • build large molecules from many smaller ones (e.g. building starch from glucose molecules)
     • change one molecule into another (e.g. converts one type of sugar into another)
     • break down large molecules into smaller ones (e.g. all the digestive enzymes of this)

2. Factors affecting enzyme action

   • Enzyme reactions are similar to other reactions when the temperature is increased
   • Reactions take place faster when it is warmer
   • At high temperatures the molecules move around more quickly and so collide with each other more oftener and with ore energy
   • If the temperature gets too hot, the enzyme stops working because the active site changes shape
     • Denatured
   • Each enzyme works bets at a particular pH value
   • Some work best in acidic conditions, but others need more neutral or alkaline conditions
   • If the pH is too acidic or alkaline for the enzyme, then the active site could change chaos
     • Denatured

3. Enzymes in Digestion

   • Some enzymes work outside body cells
   • Digestive enzymes are produced by specialised cells in glands and the lining of the gut
   • The enzymes pass out of the cells and come into contact with the food
   • Digestion involves the breakdown of large, insoluble molecules into smaller, soluble molecules
   • Amylase
     • A carbohydrase is produced by salivary glands, the pancreas and the small intestine
     • Amylase catalyses the breakdown of starch into sugars in the mouth and small intestine
   • Protease
     • Produced by the stomach, the pancreas and the small intestine
     • Catalyses the breakdown of proteins into amino acids in the stomach and small intestine
   • Lipase
     • Produced by the pancreas and small intestine
     • Lipase catalyses the breakdown of lipids (fats and oils) to fatty acids and glycerol

4. Speeding up Digestion

   • Protease enzymes in the stomach work best in acidic conditions
   • Glands in the stomach wall produce hydrochloric acid to create very acidic conditions
   • Amylase and lipase work in the small intestine
   • They work best when the conditions are slightly alkaline
   • The liver produces bile that is stored in the gall bladder
   • The alkaline bile is squirted into the small intestine and neutralises stomach acid
   • Bile makes the conditions in the small intestine slightly alkaline

5. Making use of enzymes

   • Some microorganisms produce enzymes that pass out of their cells
   • These enzymes can have many uses in industry but can also be costly to produce
   • Biological Detergents
     • Biological detergents contain proteases and lipase that digest food stains
     • Work best at lower temperatures than ordinary washing powers - saves energy and money
   • Proteases are used to pre-digest proteins in some baby foods
   • Isomerase
     • Isomerase is used to convert glucose syrup into fructose syrup
     • Fructose syrup is much sweeter, so less is needed in foods - less fattening
   • Carbohydrase are used to convert starch into sugar syrup for use in food
   • In industry, enzymes are used to bring about reactions at normal temperatures and pressures
   • Traditional chemical processes require expensive equipment and a lot of energy to produce high temperatures and pressures

6. High-Tech Enzymes

   • + enzymes in biological washing powders are very effective at removing stains such as blood, grass and gravy
   • + biological washing powders can be used at low temperatures - saving energy and reducing cost
   • + some enzymes are used in medicine to diagnose, control or even sure disease
   • + in industry, the cost of equipment and energy can be reduced
   • - if people misuse washing powders, they may have allergic reactions on their skin
   • (enzymes are enclosed in capsules in the dry powder - once the powder dissolves, hands should not be placed in the water)
   • - enzymes may enter waterways and sewage systems
   • - industrial enzymes can be costly to produce
   • - enzymes denature at high temperatures needed to kill pathogens in the washing
   • - some fabrics such as well will be digested by proteases