Enzymes

• Chemical reactions are what make you work and enzymes are what make them work
• Enzymes

  Catalysts produced by living things
• Enzymes

  • Molecules that catalyse reactions for biological processes
  • Made up of protein molecules, containing 100 - 1,000 amino acids
• Chemical Digestion


  Breaking down of larger food complex particles into smaller particles
• Enzymes

  • Amylase - found in the saliva, breaks down the starch
  • Trypsin - breaks down complex amino acids into simple sugars
  • Maltase - breaks down maltose into glucose
• Amino acids


  Joined together in a long chain to produce a unique 3D structure, an enzyme
• Catalyst


  A substance which increases the speed of a reaction, without being changed or used up in the reaction
• Living things have thousands of different chemical reactions going on inside them all the time
• Raising the temperature

  Speeds up the useful reactions but also the unwanted ones too
• Enzymes

  Biological catalysts that reduce the need for high temperatures and only speed up the useful chemical reactions in the body
• Enzymes catalyse reactions in both animals and plants — including photosynthesis in plants
• Enzymes

  • Have special shapes so they can catalyse reactions
  • Chemical reactions usually involve things either being split apart or joined together
• Substrate


  The molecule changed in the reaction
• Active site


  The part where the enzyme joins onto its substrate to catalyse the reaction
• Lock and key


  The enzyme is the lock and the substrate is the key. They fit together exactly. Once they fit together, the reaction occurs. The products leave
• Enzymes usually only work with one substrate
• Specificity


  Enzymes are said to have a high specificity for their substrate because the substrate has to fit into the active site for the enzyme to work
• Enzymes in industry

  • Washing detergents - protease and lipase
  • Baking - using yeast cells
  • Isomerase - changing glucose into fructose
  • Baby foods - predigest proteins
  • Brewing - using yeast cells
  • Carbohydrase - convert starch into sugar
• Temperature, pH and substrate concentration affect the rate of reaction
• The active site will be affected by the temperature and pH, if the conditions are NOT right
• Investigating how temperature affects enzyme activity

  1. Add a buffer solution with a different pH level to different tubes containing the enzyme-substrate mixture

  2. Vary the initial concentration of the substrate to investigate the effect of substrate concentration

  3. Vary the initial concentration of the enzyme to investigate the effect of enzyme concentration

  4. Measure how fast a product appears
• Catalase experiment

  • The enzyme catalase catalyses the breakdown of hydrogen peroxide into water and oxygen
  • You can collect the oxygen and measure how much is produced in a set time
• Measuring how fast a substrate disappears

  1. The enzyme amylase catalyses the breakdown of starch to maltose

  2. It's easy to detect starch using an iodine solution - if starch is present, the iodine solution will change from browny-orange to blue-black

  3. Use continuous sampling to record how long it takes for the amylase to break down all of the starch
• Rate of reaction


  A measure of how much something changes over time, calculated by dividing the amount that something has changed by the time taken for the change to happen
• Once bound, the substrate undergoes chemical changes due to interactions with amino acid side chains within the active site.
• Temperature

  Changing the temperature changes the rate of an enzyme-catalysed reaction.

  • A higher temperature increases the rate at first.
  • The enzymes and substrate have more energy, so they move about more and are more likely to collide and form enzyme-substrate complexes.
  • But if it gets too hot, some of the bonds holding the enzyme together break.
  • This changes the shape of the enzyme's active site, so the substrate won't fit any more.
  • The enzyme is said to be denatured.
  • All enzymes have an optimum temperature at which they work best.

  
• pH

  If it's too high or too low, the pH interferes with the bonds holding the enzyme together.

  • This changes the shape of the active site and denatures the enzyme.
  • All enzymes have an optimum pH that they work best at.
  • It's often neutral pH 7, but not always.

  
• The active site will be affected by the temperature and pH, if the conditions are NOT right.
• Substrate concentration 

  The higher the substrate concentration, the faster the reaction. 

  • This is because it's more likely that the enzyme will meet up and react with a substrate molecule.
  • This is only true up to a point though. After that, there are so many substrate molecules that the enzymes have about as much as they can cope with (all the active sites are full), and adding more makes no difference.

  
• To calculate the rate for this experiment, use the formula: 

  1 divided by time taken (in s).

  The units will be s-1