B2- Enzymes

B2- Enzymes

1. PROTEINS, CATALYSTS AND ENZYMES

   • Protein molecules are made of long chains of amino acids. The long chains are folded into specific shapes. The shape of a protein depends on its function.
   • Proteins can be: structural components of tissue, such as muscle, hormones, antibodies or 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 an area where other molecules can fit- the ACTIVE SITE.
     • The SUBSTRATE in a reaction can be held in the active sit 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 one e.g convert one type of sugar into another. Break down the large molecules into smaller ones e.g all the digestion enzymes do this.

2. FACTORS AFFECTING ENZYME ACTION

   • Enzyme reactions are similar to other reactions when the temperature is increased.
   • Reactions take place faster when its warmer. At higher temperatures the molecules move around more quickly and so collide with each other more often, and with more energy.
   • If the temperature gets too hot the enzyme stops working because the active sight changes shape. We say the enzyme becomes DENATURED.
   • Each enzyme works best at a particular pH value. Some work best in acid conditions, such as the stomach but others need neutral or alkaline conditions. If the pH is too acidic or alkaline for the enzyme, then the actice sight could change shape. Then the enzyme becomes denatured.

3. ENZYMES IN DIGESTION

   • Some enzymes work outside the body cells. Digestion enzymes are produced by specialised cells in glands and in the lining of the gut. The enzymes pass out of the cells and come into with the food. DIGESTION involves the breakdown of large, insoluble molecules into smaller soluble molecules.
   • Each reaction in controlled by a specific enzyme:
     • AMYLASE (CARBOHYDRASE)- is produced by the salivary glands, the pancreas and the small intestine. Amylase catalyses the digestion of starch into sugars in the mouth and small intestine.
     • PROTEASE- is produced by the stomach, the pancreas and the small intestine. Protease catalyses the breakdown of proteins into amino acids in the stomach and small intestine.
     • LIPASE- is 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 acid conditions. Glands in the stomach 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 the stomach acid. Bile makes the conditions in the small intestine slightly alkaline.

5. MAKING USE

   • Enzymes have many uses in industry but can be costly to produce.
   • BIOLOGICAL DETERGENTS- contain proteases and lipases that digest food stains. They work at lower temps- saves energy.
   • ISOMERASE- used to convert glucose syrup into FRUCTOSE SYRUP. Fructose is much sweeter, less needed in foods. Food then not as fattening.

6. HIGH-TECH ENZYMES

   • ADVANTAGES- Bio detergents very effective in removing stains, used at low temps, enzymes used in medicines.
   • DISADVANTAGES- Costly, denature at high temps, may enter waterways.