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
- 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
- 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
- Many species' successful egg development is dependent on temperature, with impacts such as
- 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
- 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