Factors affecting enzyme activity

• What should you be able to describe by the end of the video?

  The effect of temperature on enzymes
• What does the temperature coefficient refer to?

  The rate change with a 10°C increase
• What does the rate of enzyme-controlled reactions depend on?

  The frequency of successful collisions
• How can you calculate the rate of an enzyme-controlled reaction?

  By plotting product amount against time
• What happens to the rate of reaction as temperature increases to 40°C?

  The rate of reaction increases
• What occurs at 50°C in enzyme reactions?

  The reaction rate becomes much slower
• What is the optimum temperature for human enzymes?

  About 40 degrees Celsius
• What happens to enzymes from bacteria in hot springs?

  They have an optimum temperature of 70-80°C
• What happens to enzyme molecules at higher temperatures?

  They vibrate more rapidly, causing bond breakage
• What is denaturation in enzymes?

  Loss of function due to shape change
• Can a denatured enzyme renature when cooled?

  No, it cannot renature
• What is the temperature coefficient also known as?

  Q10
• How is the temperature coefficient calculated?

  Rate at higher temperature divided by lower rate
• What generally happens when temperature increases by 10°C?

  The rate of reaction doubles
• What happens to enzymes above their optimum temperature?

  They denature and lose function
• What is the relationship between temperature and enzyme activity?

  • Rate increases with temperature up to optimum
  • Optimum temperature for human enzymes is ~40°C
  • Higher temperatures lead to denaturation
• What are the steps to investigate the effect of temperature on enzyme activity?

  1. Select an enzyme
  2. Measure product formed over time
  3. Repeat at different temperatures
  4. Draw tangents to measure reaction rates
• What are the consequences of enzyme denaturation?

  • Active site shape changes
  • Substrate cannot bind
  • Loss of enzyme function
  • Cannot renature after denaturation
• What should you be able to describe and explain by the end of the video?

  The effective pH on enzymes
• How does the rate of an enzyme-catalyzed reaction depend on temperature?

  It works fastest at the optimum temperature
• What happens to the enzyme's tertiary structure above the optimum temperature?

  It changes, causing denaturation
• What does it mean when scientists say an enzyme is denatured?

  The active site is no longer complementary to the substrate
• What does the pH of a solution depend on?

  The concentration of hydrogen ions
• What is the relationship between pH and hydrogen ion concentration?

  A low pH has a high concentration of hydrogen ions
• What is the optimum pH for the enzyme mentioned in the video?

  Around seven
• What happens to the rate of reaction if the pH changes away from the optimum?

  The rate of reaction decreases
• How do hydrogen ions affect the bonding of amino acids in enzymes?

  They can bond with R groups, disrupting bonds
• What can happen if the pH changes significantly?

  The active site may change shape significantly
• What is the equation to calculate pH from hydrogen ion concentration?

  pH = -log[H⁺]
• How do you calculate the pH of a solution with a hydrogen ion concentration of $3 \times 10^{-8} \text{ moles per decimeter cubed}$?


  pH = 7.52
• What is the first step to calculate the pH from hydrogen ion concentration?

  Enter the concentration into the calculator
• What should you avoid pressing when calculating pH?

  The ln button
• What is the pH of a solution with a hydrogen ion concentration of $6 \times 10^{-7} \text{ moles per decimeter cubed}$?


  pH = 6.22
• What are the effects of pH on enzyme activity?

  • Each enzyme has an optimum pH
  • Deviation from optimum decreases reaction rate
  • Hydrogen ions can disrupt bonding in enzymes
  • Significant pH changes can denature enzymes
• How do you calculate pH from hydrogen ion concentration?

  1. Enter concentration into calculator
  2. Press the log button
  3. Reverse the sign of the result