4.2 - Factors affecting enzyme activity Flashcards
What must happen for an enzyme to catalyse a reaction?
The enzyme must come into contact with the substrate, and the enzyme’s active site must be the correct shape and complementary to the substrate.
How can the structure of an enzyme be affected?
The structure of an enzyme can be affected by factors such as temperature and pH, which can cause changes in the shape of the enzyme’s active site.
How do temperature and substrate concentration affect enzyme activity?
Enzymes are more likely to come into contact with the substrate and catalyze reactions when the temperature and substrate concentration are increased.
How can the effects of different factors on enzyme action be investigated?
The effects of factors on enzyme action can be investigated by measuring the rate of the reaction catalyzed by the enzyme.
What 5 factors affect the rate of enzyme-controlled action?
- Enzyme concentration
- Substrate concentration
- Concentration of inhibitors
- pH
- Temperature
How does increasing temperature affect enzyme activity?
Increasing temperature increases the kinetic energy of particles, causing them to move faster and collide more frequently, which leads to more successful collisions between the enzyme and substrate, increasing the rate of reaction.
What is the temperature coefficient (Q10)?
The temperature coefficient (Q10) is a measure of how much the rate of a reaction increases with a 10°C rise in temperature. For enzyme-controlled reactions, this is usually taken as 2, meaning the rate of reaction doubles with a 10°C increase in temperature.
Why are enzymes affected by temperature?
Enzymes are proteins, and their structure is affected by temperature. As temperature increases, the bonds holding the protein together vibrate more, and the vibrations can cause the bonds to strain and break.
What happens when the bonds in an enzyme break due to high temperature?
When the bonds break, the enzyme undergoes a change in its tertiary structure, which alters its shape. This is called denaturation.
What happens to the enzyme’s active site during denaturation?
The active site changes shape and is no longer complementary to the substrate, meaning the substrate can no longer fit into the active site, and the enzyme can no longer function as a catalyst.
What is the optimum temperature for an enzyme?
The optimum temperature is the temperature at which an enzyme has the highest rate of activity.
Do all enzymes have the same optimum temperature? Give 3 different examples.
No, the optimum temperature of enzymes can vary. For example, many human enzymes have an optimum temperature of around 40°C, while thermophilic bacteria have enzymes with an optimum temperature of 70°C, and psychrophilic organisms have enzymes that work best below 5°C.
What happens to enzyme activity when the temperature exceeds the optimum temperature?
When the temperature exceeds the optimum, the enzyme begins to denature, and the rate of reaction decreases rapidly. A slight change in the shape of the active site makes it no longer complementary to the substrate, causing a loss of enzyme function.
Why is the decrease in enzyme activity rapid above the optimum temperature?
The loss of enzyme activity is rapid because all enzyme molecules denature at about the same temperature, leading to an abrupt change in activity.
Why does the decrease in enzyme activity below the optimum temperature happen more slowly?
Below the optimum temperature, the enzymes do not denature; they just become less active, leading to a slower decrease in the rate of reaction.
Does the temperature coefficient (Q10) apply after enzyme denaturation?
No, once the enzymes denature above the optimum temperature, the temperature coefficient (Q10) no longer applies, as the enzymes are no longer functional.
How have most living organisms evolved to cope with temperature extremes?
Most organisms have evolved to survive within a certain temperature range, but some organisms are specifically adapted to cope with extreme temperatures.
What are examples of extremely cold environments where organisms live?
Examples of cold environments include deep oceans, high altitudes, and polar regions.
How are enzymes of organisms in cold environments adapted to cold temperatures?
Enzymes in cold environments tend to have more flexible structures, particularly at the active site, making them less stable. This flexibility makes them more sensitive to temperature changes and more likely to denature with smaller temperature changes.
What are thermophiles and where do they live?
Thermophiles are organisms adapted to live in very hot environments, such as hot springs and deep-sea hydrothermal vents.
