Enzymes

• What are enzymes?

  Catalysts produced by living things. (biological catalysts)
• What is a catalyst?


  A substance which increases the speed of a reaction, without being changed or used up within the reaction.
• What are enzymes made up of?


  Large proteins (proteins are all made up of chains of amino acids - these chains are folded into unique shapes, which enzymes need to do their jobs).
• Why do reactions within living things need to be carefully controlled?

  To get the right amounts of substances.
• What would happen if you were to increase the temperature of a reaction occurring within the body?

  This would speed up the useful reactions, but also the unwanted ones - there's also a limit to how far you can raise the temperature inside a living creature before its cells begin getting damaged.
• What is the substance that an enzyme acts on called?

  Substrate.
• What does every enzyme have?

  An active site with a unique shape that fits onto the substrate involved in a reaction.
• How many reactions do enzymes usually catalyse?

  One.
• What happens if the substrate doesn't fit into the enzyme's active site?


  The reaction isn't catalysed.
• What is the model called that describes an enzyme catalysing a reaction?


  Lock and key model.
• What will changing the temperature do to an enzyme-catalysed reaction?


  Change the rate.
• What happens if the temperature is increased too much in an enzyme-catalysed reaction?

  Some of the bonds holding the enzyme together will break. This changes the shape of the enzyme's active site, so the substrate won't fit any more. The enzyme is now denatured.
• What is the temperature called where the enzyme is most active?

  The optimum temperature.
• What does pH interfere with? (In terms of enzymes.)

  If it's too high or low, the pH interferes with the bonds holding the enzyme together. This changes the shape of the active site and denatures the enzyme.
• What is pepsin?

  An enzyme used to break down proteins in the stomach.
• What pH does pepsin work best at?

  pH 2.
• What does pepsin's low optimum pH mean?

  It is well suited to the acidic conditions in the stomach.
• All enzymes have an optimum pH that they work best at. It's often neutral pH 7 but not always.