Biological molecules and enzymes

• What is an enzyme?

  An enzyme is a biological catalyst that speeds up metabolic reactions without being used up.
• Elements for carbohydrate and lipids

  OHC, Oxygen, hydrogen and carbon
• Test for glucose

  • Benedicts test
  • water bath at 75 degrees celsius
  • Benedict's solution
  • Brick red(high concentration)
• Elements present in biological molecules

  • Carbohydrates: Carbon, Hydrogen and Oxygen
  • Lipids: Carbon, Hydrogen and Oxygen
  • Proteins: Carbon, Hydrogen, Oxygen and Nitrogen
• Starch

  One glucose molecule
• lipid

  Glycerol and fatty acids
• protein

  amino acid
• Starch test


  1. Take a small drop of mashed food and put it in a dropping tile

  2. Add a couple of drops of iodine solution and record any colour change

  3. If starch is present, you will see a blue-black colour
• Benedicts Test (for glucose)


  1. Take a few drops of your mashed food and put it into a boiling tube

  2. Add a few drops of Benedicts solution so that the solution goes blue

  3. Place the boiling tube into a water bath at 80°C

  4. Record the colour change that takes place after 2-3 minutes

  5. If glucose is present you will see an orange/brick-red colour
• Enzymes

  Biological catalysts that control all reactions in a cell
• Catalysts

  • Speed up a reaction without being used up
• Temperature increases


  Rate of reaction of an enzyme increases as more collisions occur between the substrate and the enzyme
• Too much heat

  Denatures the enzyme by altering the shape of its active site, so the enzyme is unable to bind to the substrate and a reaction will not take place
• Denatured enzyme

  Unable to bind to its substrate, so no reaction
• Change in the optimum pH for an enzyme

  Alters the active site of the enzyme, so a reaction will not take place as the enzyme is denatured
• Investigate how enzyme activity can be affected by changes in temperature (CORMS)

  1. Incubate amylase with starch at different temperatures

  2. Use the same type of amylase

  3. Repeat the experiment for each of the different temperatures used

  4. Measure amount of starch remaining each minute (using the starch test) for 10 minutes

  5. Keep the pH, volume of amylase and volume of starch the same