To make sure our enzyme experiments are spot on, we need to measure accurately and repeat our experiments. 🧪

• Independent Variables

  • Factors being investigated.
  • Deliberately changed to see effects.
  • E.g. temperature, substrate concentration, pH.
  • Think of it as the “cause” in cause-and-effect.

  🌡️ Real-world example: Picture making a cup of tea. If you want to see how temperature affects how quickly a tea bag steeps, you change the water temperature (that’s your independent variable)!

• Control Variables

  • Must stay the same.
  • Ensure a “fair test”.
  • Everything except the independent variable in an enzyme experiment.

  💡Tip: It's like making sure the wind doesn't interfere in your outdoor ping pong game.

• Dependent Variables

  • The results!
  • E.g. reaction rate or enzyme activity.
  • The “effect” in cause-and-effect.

  💧Example: In our tea scenario, this would be the color or strength of your tea!

• How do we calculate? Measure speed at which substrates turn into products.

• Units: change in amount of chemical divided by time, like mmols^(-1).

• Methods

  • Set time, measure substrate or product.

  • Start with substrate and measure time to complete reaction.

• 🍕 Real-world example: Think of how fast you eat a pizza slice. If you eat half in 1 min, your "reaction rate" is 0.5 slices/min!

• What’s Catalase? Enzyme that turns toxic hydrogen peroxide into water + oxygen.

• Sources? Yeast, liver, kidney, seeds.

• How to measure its activity? Check apparatus in Figure 19.

• Things to ponder

  🐱 Fun fact: Your pet cat’s liver has catalase! But please, no liver experiments on Mr. Whiskers.

  • How is catalase activity measured in Figure 19?
  • What stays constant when checking substrate concentration?
  • How to dilute 0.8 moldm^(-3) hydrogen peroxide to get 0.2, 0.4, and 0.6 moldm^(-3)?
  • Why macerate (smash up) liver before measuring its catalase?