BIOLOGY- Enzymes

• Enzymes


  Catalysts made by living organisms
• Enzymes


  • They are large proteins made up of long chains of amino acids
  • They can fold into different shapes, each shape catalysing a particular chemical reaction
• How enzymes work


  1. Enzyme has an active site with a unique shape

  2. Substrate fits into active site

  3. Enzyme speeds up the chemical reaction
• Substrate


  Reactant in a chemical reaction
• Products


  Smaller pieces that a substrate is broken into
• Enzymes speed up chemical reactions without being changed or used up in the process
• Lock and key model


  • Substrate has to fit perfectly into the active site of the enzyme
• Induced fit model


  • Enzyme changes shape slightly to better fit the substrate
• The active site of an enzyme is complementary to the substrate
• The induced fit model is more realistic than the lock and key model
• Enzymes allow living cells to carry out a huge number of chemical reactions every second
• Most chemical reactions are naturally quite slow
• Increasing temperature


  Can increase the rate of chemical reactions
• High temperatures can damage cells and speed up unwanted reactions
• Catalyst


  A substance that increases the speed of a chemical reaction without being changed or used up in the process
• Enzymes are a type of biological catalyst
• Enzymes


  Essential for helping us break down the large molecules that we eat into the much smaller soluble molecules that we can absorb through our intestinal lining
• 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
• How temperature and pH affect the functioning of enzymes and the rate of enzyme controlled reactions

  1. Temperature increases

  2. Rate of reaction increases

  3. Temperature reaches 37 degrees

  4. Rate of reaction starts to drop rapidly

  5. Enzyme becomes denatured at around 45 degrees

  6. Optimal temperature is 37 degrees
• Denatured

  Enzyme's shape changes so it can no longer bind to the substrate and catalyze the reaction
• Optimal temperature

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

  1. pH gets too high or too low

  2. Bonds holding the enzyme together start to break

  3. Active site changes shape

  4. Substrate can no longer fit

  5. Enzyme becomes denatured
• Optimal pH

  pH at which the enzyme works best
• 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 because they need to function in the stomach's acidic environment