3.1.4.2 Enzymes Flashcards
Describe what is meant by an enzyme
- Enzymes are biological catalysts, which lower the activation energy of a reaction, enabling it to occur more quickly
- Enzymes are not used up
Describe what an enzyme controlled reaction is determined by
- The number of enzyme substrate complexes that form
- The more enzyme substrate complexes that form, the lower the
activation energy of the substrate, and therefore the faster the rate of reaction.
What are the 4 factors that affect the rate of an enzyme controlled reaction
- Temperature
- PH
- Enzyme concentration
- Substrate concentration
Explain the induced fit model of enzyme action
- Initially, the enzyme’s active site and substrate are not exactly complementary.
- When the substrate binds to the active site, the active site changes shape, so that it’s complementary to the substrate.
- As the active site changes shape, stress is placed on the bonds of the substrate, lowering the activation energy of the reaction.
Describe and explain the graph showing the relationship between enzyme activity and temperature
- As the temperature increases, the rate of reaction increases because particles gain more KE, and so collisions between the substrate and active site are more likely to occur. This means that more enzyme substrate complexes form.
- As the temperature increases above the optimum, the hydrogen bonds in the tertiary structure are overcome, causing the shape of the tertiary structure, and therefore the active site to change. This means that the active site is no longer complimentary to the substrate, and so less enzyme substrate complexes form.
Describe and explain the graph showing the relationship between enzyme activity and pH
- Changes in hydrogen ion concentration in the external
solution, can change the charges of the amino acids present, which affects the hydrogen and ionic bonds in the tertiary structure. This changes the shape of the tertiary structure, as well as the shape of the active site, so it’s no longer complimentary to the active site, therefore less enzyme substrate complexes form.
Describe and explain the graph showing the relationship between enzyme activity and enzyme concentration
- As the enzyme concentration increases, the rate of reaction also increases. This is because there are more active sites, and therefore more enzyme substrate complexes form
- However, as the enzyme concentration increases further, the rate of reaction plateaus. This is because the substrate concentration
becomes the limiting factor, and so no additional enzyme substrate complexes can form.
Describe and explain the graph showing the relationship between enzyme activity and substrate concentration
As the substrate concentration increases, the rate of reaction
also increases because more enzyme substrate complexes form. However, as the substrate concentration increases further, the rate of reaction plateaus because the enzyme
concentration becomes the limiting factor, and so no additional enzyme substrate complexes form.
Describe what enzyme inhibitors do
Inhibitors reduce enzyme activity, either permanently or temporarily
What are the 2 types of inhibitors
- Competitive
- Non-competitive
Explain competitive inhibition of enzymes
In competitive inhibition, the inhibitor has a similar shape to the substrate, so it’s able to bind to the active site in place of the substrate. Therefore, fewer enzyme substrate complexes form because the active site is blocked by the inhibitor.
Describe how the effects of competitive inhibition can be reduced
- Increasing the substrate concentration
Explain non-competitive inhibition of enzymes
In non-competitive inhibition, the inhibitor doesn’t bind to the
active site. Instead, it binds to another part of the enzyme called the allosteric site, which causes the shape of the tertiary structure to change, which changes the shape of the active
site. Therefore, fewer enzyme substrate complexes form since
the active site and substrate are no longer complimentary
Explain why increasing the substrate concentration does not reduce the effect of non-competitive inhibition
Non-competitive inhibitors do not compete for the active site
Sucrase does not hydrolyse lactose. Use your knowledge of
the way in which enzymes work to explain why.
- Enzymes have a specific shape which is complementary to their substrates.
- Lactose has a different structure/shape to sucrose and therefore lactose will not bind to the active site of sucrase.