Enzymes

• Enzymes are biological catalysts that speed up chemical reactions in the body
• They are large proteins made up of chains of amino acids, which are folded into unique shapes
• Every enzyme has an active site which is complementary to fit onto the substance
• Induced fit - the enzyme changing its active site to get a tighter fit
• Changing the temperature changes the rate of an enzyme catalysed reaction
• If temperature becomes too high, the enzymes active site changes and the substrate no longer fits, it has become denatured
• The optimum temperature is where the enzyme is most active
• The pH also affects enzymes, if its too high or too low the bonds holding the enzyme together are interfered with. The shape of the active site is changed so the enzyme is denatured
• The optimum pH is often 7
• Digestive enzymes break down large molecules, such as starch, proteins and fats.
• Amylase is a carbohydrase, it breaks down starch into simple sugars
• Amylase is made in the salivary glands, the pancreas and the small intestines
• Proteases convert protiens into amino acids
• Protease is made in three places, the stomach (called pepsin there), the pancreas and the small intestines
• Lipases convert lipids into glycerol and fatty acids
• Lipases are made in the pancreas and the small intestines
• Bile neutralises the stomach acid and emulsifies fats
• Bile is produced in the liver, its stored in the gall bladder before its released into the small intestines
• The hydrochloric acid in the stomach makes the pH too acidic for the enzymes in the small intestine to work properly, bile is alkaline so it neutralises the acid and makes conditions alkaline
• It breaks down fats into tiny droplets, this gives a much larger surface area of fat for the lipase to work on, so digestion is faster
• Protease works best at pH 2