enzymes

• enzymes


  proteins molecules that act as biological catalysts
• enzymes are made up of...

  long chains of amino acids
• enzymes are biological...


  catalysts
• catalyst


  substance that speeds up the rate of a chemical reaction without being changed or used up in the reaction
• enzymes have ... shapes so they can catalyse reactions

  unique
• why do enzymes have unique shapes?

  because different enzymes have differently shaped active sites
• each enzyme has an....

  active site
• what is the active site?

  the active site is the region on the enzyme where the substrate binds
• why are active sites uniquely shaped?

  the shape of the active site of an enzyme is complementary to the shape of its specific substrate - this means they are the correct shapes to fit together
• the ... fits into the active site

  substrate
• what is the substrate?

  the substance on which an enzyme acts
• lock and key model

  the model of the enzyme that shows the substrate fitting perfectly into the active site and the substrate breaking up into products while the enzyme is unchanged

  
• what affects enzyme action?

  - temperature

  - pH

  - substrate/enzyme concentration
• every enzyme has an optimum...

  temperature and pH
• what is the optimum temperature for (most) enzymes?

  37°C
• what happens if the temperature is too low for enzymes?

  enzyme activity is low because the enzyme and substrate molecules have less kinetic energy so there are fewer collisions between them
• what happens if the temperature is too high for enzymes?

  some of the bonds holding the enzyme together break, changing the shape of the enzyme's active site, so the substrate won't fit anymore (this results in the enzyme denaturing)
• denature


  a change in the shape of a protein (such as an enzyme) that can be caused by changes in temperature or pH (among other things)
• what is the optimum pH for (most) enzymes?

  7 (neutral)
• what happens if the pH is too low/high for enzymes?

  some of the bonds holding the enzyme together break, changing the shape of the enzyme's active site, so the substrate won't fit anymore (this results in the enzyme denaturing)
• effect of pH on enzyme activity practical

  1. set up a Bunsen burner, heatproof mat, tripod and gauze

  2. place a beaker of water on the gauze and adjust the flame to keep the water at about 35°C

  3. now put two drops of iodine solution into each spot of a spotting tile

  4. add 2 cm3 of amylase enzyme solution to a test tube

  5. place 2 cm3 of starch solution into the same tube

  6. finally add 1 cm3 of pH solution to the tube. This will keep the pH constant

  7. mix the solution in the test tube and place it into the beaker of water on the Bunsen burner

  8. use a pipette to remove a few drops of solution every 20 seconds from the test tube and put them into a different well of the spotting tile

  9. repeat until the iodine solution stops turning black

  10. record the time this takes

  11. repeat with different pH solutions
• rate of reaction formula (in effect of pH on enzyme activity practical)

  rate = 1000/time