Enzymes

• Enzymes

  Biological catlysts that speed up reactions without being changed or used up
• Enzymes


  • They are large proteins made up of long chains of amino acids
  • The amino acid can fold into different shapes, each shape being a unique enzyme that catalyzes a particular chemical reaction
• How enzymes work

  1. Enzyme has an active site with a unique shape complementary to the substrate

  2. Substrate binds to active site

  3. Enzyme catalyzes the reaction

  4. Products are released
• Substrate


  Reactant in a biological chemical reaction
• Products


  Smaller pieces that a substrate is broken into during a reaction
• Catalyst


  A substance that increases the speed of a chemical reaction without being changed or used up in the process
• Most chemical reactions are naturally quite slow


  Enzymes speed up the reactions
• Increasing temperature to speed up reactions in the body


  Requires a lot of energy, can damage cells, and speeds up unwanted reactions
• Lock and key model

  • Substrate has to fit perfectly into the active site of the enzyme, like a key in a lock
• Induced fit model


  • Enzyme changes shape slightly to better accommodate the substrate, like a hand fitting into a rubber glove
• How temperature and pH affect the functioning of enzymes and the rate of enzyme controlled reactions

  1. Increase in temperature increases rate of reaction

  2. Rate starts to drop rapidly at high temperatures due to bonds breaking and active site changing shape

  3. Enzyme becomes denatured at high temperatures

  4. Optimal temperature is the temperature at which rate of reaction is highest
• Denatured


  Enzyme cannot bind to substrate and catalyze reaction anymore due to active site changing shape
• Optimal temperature


  Temperature at which rate of reaction is highest
• How pH affects enzymes

  1. If pH gets too high or too low, it will lower the rate of reaction

  2. At first, active site just changes a bit so substrate can still fit but less well

  3. Soon, active site changes shape so much that substrate can't fit at all and enzyme becomes denatured
• Optimal pH


  pH at which enzyme works best, depends on where enzyme normally works
• Most enzymes in our body work best at neutral pHs of around 7
• Enzymes that work in the stomach have an optimal pH of around 2 to function in the acidic environment
• Main groups of nutrients to be broken down

  • Carbohydrates
  • Proteins
  • Fats
• Carbohydrates


  Found mainly in foods like pasta, potatoes and rice, used by the body mainly as an energy source
• Starch


  The main type of carbohydrate
• Breakdown of starch


  Broken down by the enzyme amylase into smaller sugars such as maltose
• Places where amylase is made

  • Salivary glands
  • Pancreas
  • Small intestine
• Proteins


  Found in things like nuts, meats and beans
• Breakdown of proteins


  Broken down by protease enzymes into amino acids
• Places where proteases are made

  • Stomach (pepsin)
  • Pancreas
  • Small intestine
• Fats/Lipids


  Found in foods like cheese, oils and chocolate
• Breakdown of fats/lipids


  Broken down by lipase enzymes into glycerol and fatty acids
• Places where lipases are made

  • Pancreas
  • Small intestine
• All digestive enzymes are made by the pancreas and small intestine, with amylase also made by salivary glands and proteases also made in the stomach