Graphs

• Graph 1

  • As time passes oxygen volume produced increases
  • Directly proportional
  • Positive correlation
  • Fastest rate of oxygen production is first 30 seconds
  • Linear
  • After 4.5cm^3 oxygen is produced
  • Now, oxygen production rate begins to decrease
  • Volume levels off after two minutes at ~9.5cm^3

  
• Graph 2

  • As time increases starch mass decreases
  • Fastest rate is in first 30 seconds
  • Steep linear decrease
  • After 30 seconds mass of starch decrease rate slows down
  • After 10 minutes mass of starch reaches 0g

  
• Measuring Enzyme Activity:

  • Incubate enzyme and substrate in a test tube
  • Either measure product accumulation or substrate disappearance
  • Measurements are collected over time (time course)
• • Graph Explanation
  • First 30 seconds:
  • High substrate concentration
  • Very little product
  • More chance substrate will collide with empty active sites
  • So most active sites are occupied and product made
  • Substrate concentration is not limiting factor (in least supply)
  • After 30 seconds:
  • Substrate concentration decreases
  • More product formed
  • More difficult for fewer substrates to collide with active sites
  • Also, product molecules interfer
  • Substrate concentration limits
  • When volume of oxygen and starch mass level off, substrate has been used up and no more product can be produced
• Calculating...

  • Formula = y-axis/x-axis in cm^3min^ -1
  • Rate over first 30s
  • 6/30 = 0.2 ← in seconds, x60 to convert to minutes
  • 0.2 x 60 = 12cm^3min^ -1
  • To compare reaction rates of different or same enzymes in conditions initial rate is used
  • Initial rate is in first few seconds when its maximum
  • Dashed line shows initial rate of oxygen production
  • 9.4/30 = 0.313
  • 0.313 x 60 = 18.8cm^3min^ -1