Enzymes

What do you need to know?

  • Enzymes are biological molecules that help chemical reactions to take place faster in living organisms.
  • This practical investigates changing a factor that effects the rate of reaction. This is most commonly pH, but it could be temperature so watch out.
    • The dependent variable is the time it takes for the enzyme Amylase to break down starch into glucose. Iodine is used to test for the presence or absence of starch.
    • The independent variable is most commonly the pH. A pH buffer can be added to set the chemical reaction at an exact pH.
    • The most common control variable is the temperature which is controlled with a water bath.
    • The most common error in the experiment is the timing exactly when the reaction has been completed. You can only check this approximately every 30 seconds. This means your experiment is not very accurate
  • Forgotten your variables - review them

1. Watch the video


2. Click here to try the practical for yourself.


3. Click here for the exambank pack for this practical

Give a definition of accuracy

The ability to measure to the true value

Describe the effect of excess temperature or pH on an enzyme's shape

It changes its 3d shape and becomes denatured

State the name of the protease enzymes found in the stomach AND intestine

The stomach produces Pepsin. I remember this because Pepsin starts with a P and so does pH. There is a low pH in the stomach.

The intestines produces Trypsin (both of which have a T)

State the name of the molecule that proteins are broken down into by proteases

State the name of the molecule that lipids are broken down into by Lipases

Proteases break Proteins into amino acids

Lipases break lipids into fatty acids and glycerol