Edexcel International A Level Biology

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5.21 The Effect of Temperature on Enzyme Reactions

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The Effect of Temperature on Enzyme Reactions

  • Changing air temperature can have a significant impact on the metabolism of living organisms due to the effect of temperature on enzyme activity
  • Enzymes have a specific optimum temperature
    • This is the temperature at which they catalyse a reaction at the maximum rate
  • Lower temperatures either prevent reactions from proceeding or slow them down
    • Molecules move relatively slowly as they have less kinetic energy
    • Less kinetic energy results in a lower frequency of successful collisions between substrate molecules and the active sites of the enzymes which leads to less frequent enzyme-substrate complex formation
    • Substrates and enzymes also collide with less energy, making it less likely for bonds to be formed or broken 
  • Higher temperatures cause reactions to speed up
    • Molecules move more quickly as they have more kinetic energy
    • Increased kinetic energy results in a higher frequency of successful collisions between substrate molecules and the active sites of the enzymes which leads to more frequent enzyme-substrate complex formation
    • Substrates and enzymes also collide with more energy, making it more likely for bonds to be formed or broken 


  • If temperatures continue to increase past a certain point, the rate at which an enzyme catalyses a reaction drops sharply as the enzymes begin to denature
    • The increased kinetic energy and vibration of an enzyme puts a strain on its bonds, eventually causing the weaker hydrogen and ionic bonds that hold the enzyme molecule in its precise shape to start to break
    • The breaking of bonds causes the tertiary structure of the enzyme to change
    • The active site is permanently damaged and its shape is no longer complementary to the substrate, preventing the substrate from binding
    • Denaturation has occurred if the substrate can no longer bind

Enzyme denaturation

At high temperatures enzymes can denature

The effect of temperature on an enzyme-catalysed reaction

The rate of an enzyme catalysed reaction is affected by temperature. Note that 35 degreeC is not the optimum temperature for all enzyme-controlled reactions.

Calculating the temperature coefficient

  • The temperature coefficient, represented by Q10, calculates the increase in rate of reaction when the temperature is increased by 10 degreeC
  • Q10 can be calculated using the following equation

Q10 = rate at higher temperature divided byrate at lower temperature

  • A Q10 value of 2 indicates that the reaction rate doubles with an increase in temperature of 10 degreeC, while a value of 3 indicates that it trebles with every 10 degreeC increase

Worked example

In an enzyme catalysed reaction the rate of reaction can measured by recording the volume of product produced per unit time at different temperatures.

At 30 degreeC 3.5 cm3 s-1 of product was recorded and at 40 degreeC 6.8 cm3 s-1 was recorded. Calculate Q10 for this reaction.

Step 1: Write out the relevant equation

Q10 = rate at higher temperature divided by rate at lower temperature

Step 2: Substitute numbers into the equation

Q10 = 6.8 divided by3.5

Step 3: Complete calculation

Q10 = 1.94

This value is close to 2, indicating that the rate of reaction has almost doubled

Enzyme activity and living organisms

  • Changes to enzyme activity that result from changing global temperatures can affect living organisms
  • Some chemical reactions take place faster at higher temperatures 
    • Photosynthesis is essential for converting carbon dioxide into carbohydrates, the process which produces food for producers and other organisms higher up the food chain; it relies on the function of proteins in the electron transport chain and that of enzymes such as rubisco
      • E.g. blue-green algae, also known as cyanobacteria, photosynthesise at a higher rate in warmer water due to increased enzyme activity; this increases the formation of potentially harmful algal blooms
  • Some chemical reactions are slowed down at higher temperatures 
    • At high temperatures plants carry out a reaction called photorespiration at a faster rate; this reaction uses the enzyme rubisco and so slows down photosynthesis
      • This can reduce crop yields as temperatures rise
    • Some fish eggs have been shown to develop more slowly at higher temperatures
      • Many species' successful egg development is dependent on temperature, with impacts such as
        • Extreme temperature fluctuations can reduce hatching rates in some invertebrates
  • The sex of the young inside the egg of some species is determined by temperature, so increasing temperatures can affect the sex ratios in a species
    • E.g. in alligators
  • Species may have to change their distribution in response to changing temperatures in order to survive
    • Species may migrate to higher altitudes or further from the equator to find cooler temperatures

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Naomi graduated from the University of Oxford with a degree in Biological Sciences. She has 8 years of classroom experience teaching Key Stage 3 up to A-Level biology, and is currently a tutor and A-Level examiner. Naomi especially enjoys creating resources that enable students to build a solid understanding of subject content, while also connecting their knowledge with biology’s exciting, real-world applications.