1.7 Enzyme action

• What do enzymes do to the rate of reaction?

  They increase the rate by lowering activation energy
• What is the structure of enzymes?

  They are 3D tertiary structured globular proteins
• How is the shape of an enzyme determined?

  By the primary sequence of amino acids
• What is the active site of an enzyme?

  An area made of a few amino acids
• What is the molecule that enzymes act upon called?

  Substrate
• Why are enzymes specific to substrates?

  Only one type of substrate fits the active site
• What forms when an enzyme binds to its substrate?

  An enzyme-substrate complex
• What happens to the enzyme's structure when it binds to the substrate?

  The active site fits around the substrate
• What is the induced fit model?

  Enzyme structure alters to fit the substrate
• What factors affect the rate of enzyme-controlled reactions?

  • Temperature
  • pH
  • Enzyme concentration
• How does temperature affect enzyme activity?

  Rate increases to optimum, then decreases
• What happens to enzymes above their optimum temperature?

  They become denatured
• What does pH measure in a solution?

  The hydrogen ion concentration
• How is pH calculated?

  pH = -log10[H+]
• What pH corresponds to a hydrogen ion concentration of $1 \times 10^{-9}$?


  pH of 9
• How does pH affect enzyme structure?

  It can disrupt bonds in the tertiary structure
• What is an example of an enzyme that works in acidic conditions?

  Pepsin in the stomach
• How does enzyme concentration affect reaction rate?

  Rate increases with more active sites available
• What happens when enzyme concentration exceeds substrate concentration?

  Substrate concentration becomes the limiting factor
• What are the effects of temperature, pH, and enzyme concentration on enzyme activity?

  • Temperature: Increases to optimum, then denatures
  • pH: Affects shape, varies by enzyme
  • Enzyme concentration: Increases rate until substrates are limiting