2.5 Enzymes Flashcards
What type of protein are enzymes?
Globular
What are the three stages of enzymes?
1) The substrate binds to the active site of the enzyme. Some enzymes have two substrates that bind to different parts of the active site.
2) While the substrates are bound to the active site they change into different chemical substances, which are the products of the reaction. This reduces the energy required to reach the transition state, and therefore speeds up the reaction as more collisions have the energy to react.
3) The products separate from the active site, leaving it vacant for substrates to bind again.
What has to happen for an enzyme and a substrate to bind?
Collisions between substrate molecules and the active site occur because of random movement of both substrate and enzyme. Successful collisions are ones in which the substrate and active site are correctly aligned to allow binding to take place.
How does temperature effect an enzymes activity?
In liquids the particles are in continuous random motion. When a liquid is heated the particles get more energy and move around faster meaning more successful collisions take place, therefore the rate of reaction increases. However at a certain point the enzyme will become denatured, when the vibrations in the molecule cause intermolecular bonds to break and the shape of the molecule changes. Then the rate of the reaction will dramatically fall as the enzyme can no longer reduce the energy needed to reach the transition state.
How does pH effect enzymes?
Most enzymes have an optimum pH at which their activity is highest. If the pH is increased or decreased from the optimum, enzyme activity decreases and eventually stops altogether. When the hydrogen ion concentration is higher or lower than the level at which the enzyme naturally works the structure is altered, and beyond a certain pH it is irreversibly altered and the enzyme is denatured.
How are enzymes effected by substrate concentration?
Increasing the concentration increases the rate of reaction until a certain point. Increasing the concentration increases the frequency of collisions and therefore more enzymes are working at the same time and the rate of reaction is faster. However this is only up to a certain point, because at the point where all the active sites are occupied it cannot increase the rate of reaction any further.
What are immobilised enzymes?
This means the enzymes cannot move, they are attached to a surface. You can do this by attaching them to a glass surface, trapping them in an alginate gel or bonding them together to form enzyme aggregates of up to 0.1mm in diameter.
What are the advantages of immobilised enzymes?
- The enzyme can easily be separated from the products of the reaction, stopping the reaction at the ideal time and preventing contamination of the products.
- After being retrieved from the reaction mixture the enzyme may be recycled, giving useful cost savings, especially as enzymes are expensive.
- Immobilisation increases the stability of enzymes to changes in temperature and pH, reducing the rate at which they are degraded and have to be replaced.
- Substrates can be exposed to higher enzyme concentrations than with dissolved enzymes, speeding up reaction rates.
How do we produce lactose-free milk?
Lactose is the sugar that is naturally present in milk. It can be converted into glucose and galactose by the enzyme lactase.
Lactase is obtained from a type of yeast that grows naturally in milk.
Biotechnology companies culture this yeast extract the lactase from the yeast and purify it for sale to food manufacturing companies.
- This means lactose intolerant people can have milk
- Galactose and glucose are sweeter than lactose so less sugar needs to be used.
- Lactose tend to crystallise during the production of icecream, giving a gritty texture but because glucose and galactose are more soluble they do not, giving a smoother texture.
- Bacteria ferment glucose and galactose more quickly than lactose so the production of yoghurt and cheese is faster.
Advantages of lactose-free milk?
- This means lactose intolerant people can have milk
- Galactose and glucose are sweeter than lactose so less sugar needs to be used.
- Lactose tend to crystallise during the production of icecream, giving a gritty texture but because glucose and galactose are more soluble they do not, giving a smoother texture.
- Bacteria ferment glucose and galactose more quickly than lactose so the production of yoghurt and cheese is faster.
What is lactose?
A sugar present in milk. You can break it down into glucose and galactose.
