Temperature & Enzyme Function (Edexcel IGCSE Biology: Double Science)

• Enzymes are proteins and have a specific shape, determined by the amino acids that make the enzyme and held in place by bonds
• This is extremely important around the active site as the specific shape is what ensures the substrate will fit into the active site and enable the reaction to proceed
• Enzymes work fastest at their ‘optimum temperature’
  • In the human body, the optimum temperature is 37⁰C

• Heating to high temperatures (beyond the optimum) will break the bonds that hold the enzyme together and it will lose its shape
  • This is known as denaturation

• Substrates cannot fit into denatured enzymes as the shape of their active site has been lost
• Denaturation is irreversible - once enzymes are denatured they cannot regain their proper shape and activity will stop

Effect of temperature on enzyme activity

• Increasing the temperature towards the optimum increases the activity of enzymes as the more kinetic energy the molecules have the faster they move and the number of collisions with the substrate molecules increases, leading to a faster rate of reaction
• This means that low temperatures do not denature enzymes, they just make them work more slowly due to a lack of kinetic energy

Graph showing the effect of temperature on the rate of enzyme activity