temperature-and-enzyme-activity

Temperature & Enzyme Activity

• 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 

Denaturation

• 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

At high temperatures enzymes can denature

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

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

Practical: Temperature & Enzyme Activity

• The progress of enzyme-catalysed reactions can be investigated by measuring the rate of formation of a product 

• This can be carried out using the enzyme catalase

  • Hydrogen peroxide is a common but toxic by-product of cell metabolism which must be broken down quickly

  • Catalase is an enzyme found in the cells of most organisms that breaks hydrogen peroxide down into water and oxygen

  • The rate at which oxygen is produced can be recorded to give a measure of enzyme activity

Investigating the effect of temperature on catalase activity

Apparatus

• Boiling tubes or flasks

• Hydrogen peroxide solution

• Buffer solution

• Measuring cylinder or syringe

• Bung and delivery tube

• Water basin

• Pipettes

• Catalase enzyme solution

• Water baths at a range of temperatures

• Stopwatch

Method

1. Set up a series of water baths at different temperatures e.g. 10 C, 20 C, 30 C, 40 <img alt=”degree” data-mathml='<math class=”wrs_chemi