Biological Molecules

• Elements in Carbohydrates

  Hydrogen, Carbon, oxygen
• Lipids

  Hydrogen, Carbon, oxygen
• Protein


  Hydrogen, Carbon, oxygen, Nitrogen

  (sometimes other elements)
• Carbohydrates


  glucose, starch and glycogen - simple sugars
• Lipids


  fatty acids - glycerol
• Proteins


  amino acids
• Test For Glucose - Method

  • add drops of Benedict’s solution into test tube of test solution
  • heat test tube placed in water bath at 60-70°C for 5mins
  • remove test tube from water bath and observe colour change
• Results for test for glucose

  Blue = none

  Green = Trace

  Yellow = low

  Orange = Moderate

  Brick Red = high
• Test for Starch - method


  Use pipette to drop sample solution into spotting tile

  Add drops of iodine and observe colour change
• Results for test for starch

  if starch present orange brown → blue black
• Test for Protein - Method

  add drops Biuret solution to sample

  observe colour change
• Results for test for protein

  violet if protein is present

  blue if there is no protein
• Test for Lipids - method

  2cm^2 of ethanol and 2cm^3 of distilled water

  leave for reaction to happen

  strain test tube

  add cold distilled water
• Results for test for lipids

  is fat present - milky white emulsion will form
• Enzymes


  Biological catalysts that speeds up rate of reaction without being used up (biological because made in living cells)
• enzymes are necessary to all living organisms because they maintain reaction speeds of all metabolic reactions at a rate of that can sustain life
• what are enzymes made of

  amino acids
• how do enzymes work

  It is specific to one substrate as the active site is a complementary shape - Lock and Key method
• main factor that affects enzymes:

  temperature
• Temperature too high for enzymes

  break the bonds that hold the enzyme together and therefore its shape changes (denatures)

  substrate cannot fit

  denaturing is irreversible
• Increase temperature towards the optimum temperature

  increases the activity of enzymes - more kinetic energy makes = move faster which means more collisions with substrate molecules therefore higher rate of reaction
• Low temperatures for enzymes

  Low temperatures make enzymes work slower due to lack of energy
• Practical for enzymes


  • add 5cm^3 of starch solution to test tube and heat to set temperature using beaker of water and bunsen burner
  • add drops of iodine to wells of spotting tiles
  • add 2cm^3 of amylase to starch solution and mix well
  • every minute add a drop of solution to a new well
  • repeat until iodine stops turning blue black
  • record time taken and repeat over range of temperature
• what is the optimum pH for most enzymes

  seven
• what happens if the pH is too high or low

  the bonds that hold the amino acids together are broken
• what happens when bonds that hold amino acids together in enzyme break


  Active site shape changes so substrate no longer fits rate of reaction decreases
• what happens when an enzyme is severely denatured due to pH

  activity stops