Enzyme

Question 1

What is the lock and key model of enzyme action?

Answer 1

The way in which an enzymes active site has a specific shape meaning it is complementary to the shape of the substrate molecules.

Question 2

What level of protein structure and what shape is an enzyme ?

Answer 2

Enzymes have a tertiary structure and are globular

Question 3

How are enzymes named?

Answer 3

Most end in ase and many are named after the substrate. One important name to remember is hydrogen peroxide - catalyse…?

Question 4

How do enzymes catalyse a substrate according to the lock and key model?

Answer 4

The substrate enters the enzymes active site and the enzyme and substrate form a enzyme-substrate complex. Then the substrate leaves the enzyme now catalysed into two smaller products. The enzyme remains unchanged. It is worth noting that given the right circumstances, the enzyme can catalyse the reverse reaction.

Question 5

How does an enzyme catalysed a complementary substrate according to the induced fit model?

Answer 5

First the substrate collides with the active site. The active site fits more closely around the substrate molecule and is held in position by oppositely charged groups. An enzyme substrate complex is formed. A change in the enzyme shape places a strain on the substrate, allowing the reaction to occur at a lower activation energy. The enzyme product complex now forms. The product no longer fits into the active site and so is released. The enzyme returns to its original shape.

Question 6

Give an example of an enzyme that works in the induced fit model

Answer 6

Lysozyme

Question 7

What is activation energy?

Answer 7

The extra energy that is required to enable the action to occur. This energy is often through heat in a laboratory reaction

Question 8

How do enzymes affect activation energy?

Answer 8

Enzymes lower the activation energy of a reaction by acting as biological catalysts. This allows the reaction to proceed quickly at low temperatures in the body, so that molecules can be broken down and new ones formed.

Question 9

What is the optimum temperature of an enzyme?

Answer 9

The optimum temperature of an enzyme is always dependent on the natural environment of that enzyme.

Question 10

What happens towards the optimum temperature of an enzyme?

Answer 10

The kinetic energy of the enzymes and substrates increases. Therefore, more successful collisions, leading to more enzyme-substrate complexes and more products produced per unit of time.

Question 11

What happens above the optimum temperature of an enzyme?

Answer 11

Above the optimum temperature, there is too much kinetic energy and enzymes will vibrate. The weaker Bonds in the tertiary structure will begin to break (the ionic and hydrogen bonds). The tertiary structure will change, the shape of active site will change and the enzyme will no longer be specific . the substrate can no longer Bond to form ESC so the number of products produced per unit of time decreases as enzymes denature

Question 12

What occurred at the optimum pH?

Answer 12

The highest number of successful collisions takes place here as a result of the highest number of enzyme-substrate complexes. It is the highest rate of reaction

Question 13

What does it mean for there to be a low pH vs a high pH?

Answer 13

At a low pH number is low for example 1 and there are more hydrogen ions. At a high pH number is high for example, 14 and there are more oh ions

Question 14

Describe a ph Curve with ph on the x-axis and rate of enzyme activity on the Y

Answer 14

It is a symmetrical peak with an exponential Curve either side of the Peak. PH curves usually are much thinner than those for temperature.

Question 15

What happens either side of the optimum pH peak?

Answer 15

There is a slight change of charge within the active site of the enzyme, meaning there are less successful collisions per unit of time. There are less enzyme-substrate complexes formed per unit of time and a lower rate of reaction. This is all because the substrates are harder to fit in the enzyme because some of the changed charges will repel the substrate. However this is reversible if the pH is brought back to neutral or optimum. A buffer solution can be used for this.

Question 16

What happens in the extreme changes of pH ?

Answer 16

The change in pH causes bonds to break and the enzyme denatures. This means there is a change in the tertiary structure and so change in the specific shape of the active site. This means there are less or no successful collisions, less or no enzyme-substrate complex is forming and a low or no rate of reaction. This is not reversible

Question 17

Why are enzyme and substrate Solutions left in water baths for 5-minutes before combining and mixing?

Answer 17

To ensure the solutions are at the desired temperature

Question 18

Describe a graph that has substrate concentration on the x-axis and rate of reaction on a y axis

Answer 18

There is a steady increase and then a rather sudden change to a horizontal line plateau

Question 19

What happens at the plateau of a substrate concentration / rate reaction graph?

Answer 19

The substrate concentration increases the rate of reaction does not. All enzymes are already involved in a reaction and can accept any more substrate. Therefore increasing substrate concentration further will not increase the rate of reaction.

Question 20

What is happening at the steady increase of the substrate concentration / rate of reaction graph?

Answer 20

The substrate concentration increases and so does the rate of reaction. At this point of substrate concentration, there are enzymes not involved in catalyzing the reaction. therefore they can be made useful with more substrate, thus increasing the rate of reaction.

Question 21

Describe a graph of enzyme concentration with excess substrate present / rate of reaction

Answer 21

It is straight line increasing

Question 22

Describe what happens as the enzyme concentration increases to the rate of reaction

Answer 22

As the enzyme concentration increases, so does the rate of reaction. With excess substrate , any enzymes not involved in a reaction will instantly find substrates to catalyses increasing rate of reaction.

Question 23

What do enzyme inhibitors do? What are they?

Answer 23

They reduce the rate of reaction and they are chemicals

Question 24

How many types of inhibitors are there and what are they?

Answer 24

There are two types. They’re called competitive and noncompetitive

Question 25

What are competitive inhibitors? What do they do?

Answer 25

These are are inhibitors that have a similar but not same as shape to the substrate molecule intended for that enzyme. They enter the active site and bond with the enzyme, forming an enzyme inhibitor complex and prevent the normal substrate from entering by blocking the active site.

Question 26

How do competitive inhibitors affect the rate of reaction?

Answer 26

They reduce the rate of reaction as the number of enzyme-substrate complexes that can form is reduced. Basically, competitive inhibitors compete with the substrate for the position of the active site.

Question 27

How is the effect of inhibition determined?

Answer 27

The effect of inhibition is determined by the amount of inhibition caused by the relative concentration of substrate and inhibitor molecules. More inhibitor molecules means more inhibitors collide with active sites and so the effect of inhibition is greater.

Question 28

How does the level of inhibition change with the concentration of substrate?

Answer 28

If the concentration of substrate is increased, and the level of inhibition will decrease. Because it will increase the chance of the normal substrate binding with the active site.

Question 29

How does a substrate / rate of reaction graph compare to that of of one with an enzyme inhibitor present?

Answer 29

The graph with an enzyme inhibitor present shows a shift to the right, meaning it takes more substrate for the maximum rate of reaction to be achieved.

Question 30

How are enzyme inhibitors beneficial in end-product production ?

Answer 30

Enzyme inhibitors are beneficial because products can sometimes act as enzyme inhibitors, slowing down reactions because there are already too many products….?

Question 31

What do non competitive inhibitors do?

Answer 31

They don’t compete with substrate molecules of the active site. Instead, they attach away from the active site and distort the tertiary shape of the enzyme which leads to a change in the active site shape . this means the substrate no longer fits the active site, so enzyme-substrate complexes can’t form and the rate of reaction will decrease.

Question 32

How will increasing substrate concentration affect the rate of reaction when a non competitive inhibitor is present?

Answer 32

It will increase the rate of reaction up to a point but this point of maximum rate of reaction will be lower than if an inhibitor was not present. The enzymes will have been denatured so the maximum amount of product is never achievable.

Question 33

State examples of non competitive inhibitors

Answer 33

Cyanide, arsenic, lead, Mercury

Question 34

Are enzyme inhibitors reversible or non-reversible?

Answer 34

Competitive and noncompetitive inhibitors can either be reversible or non-reversible. Many inhibitors don’t bind permanently with active sites or away from active sites so they are described as reversible inhibitors. Others permanently bind to the active site or away from the active site and therefore are non reversible.

Question 35

Are competitive inhibitors reversible or permanent?

Answer 35

Most competitive inhibitors are reversible …?

Question 36

Are non competitive inhibitors reversible or permanent?

Answer 36

Many are permanent but those involved in control of metabolic pathways are reversible.

Question 37

Give an example of a competitive inhibitor

Answer 37

Products the enzyme has already catalysed

Question 38

Industrially, how enzymes produced?

Answer 38

Enzymes are produced by culturing microbes in fermentation vessels. The microbes produce the enzymes as part of their normal metabolic activity. The microbes are then removed and the enzymes are extracted from the culture and purified. The enzymes can then be added to the substrate molecules to catalyse reactions which would be difficult to carry out otherwise.

Question 39

How can protease be produced and what is it used for?

Answer 39

It is used for washing powder and burgers and it is produced by bacillus bacterium.

Question 40

How can glucose isomerase be produced and what is it used for?

Answer 40

By fungus streptopmycin and used for coca cola

Question 41

How can rennin be produced and what is it used for?

Answer 41

Produced my mucor fungus and used in vegan cheese

Question 42

How can pectinase be produced and what is it used for?

Answer 42

Produced by aspergillus fungus and used in orange juice

Question 43

Why are enzymes used in large-scale industrial production?

Answer 43

They are used as biological catalysts to speed up the rate of reaction. They lower activation energies meaning they ultimately lower temperatures and energy and increase efficiency. They mean there are fewer side reactions meaning there is less waste and fewer purification process stages.

Question 44

What are immobilized enzymes?

Answer 44

They are enzymes which are held or stabilized in an inert support or matrix for example cellulose

Question 45

How does the reaction work with immobilized enzymes?

Answer 45

The reaction occurs as the substrate passes over the immobilized enzymes

Question 46

Why do we immobilise enzymes ?

Answer 46

Free enzymes can be added directly to the substrate and the reaction allowed to proceed but When the products form they are contaminated with the enzymes. The enzymes then cannot be used again. However, these problems can be overcome if the enzymes are immobilized.

Question 47

What are the advantages of immobilised enzymes over free enzymes?

Answer 47

Enzymes are easily recovered reducing cost , product is not contaminated by enzyme, the polymer matrix create a micro environment for the enzyme so there is a more stable PH and temperature , they can be used in continuous processes , several enzymes with different Optima can be used at the same time.

Question 48

What are the two ways an enzyme can be immobilised?

Answer 48

They can be fixed or trapped in an inert Matrix

Question 49

Give two examples of inert matrices

Answer 49

Entrapment also called enzyme inclusion in a cellulose mesh. Encapsulation in alginate beads called microcapsules

Question 50

What are the disadvantages of immobilization?

Answer 50

In absorption the enzyme may become detached and contaminates the product. If enzymes are held within a substrate for example the alginate bead the substrate must diffuse into the gel which takes time. Free enzymes can access the substrate immediately and reaction rates are there for quicker than using immobilized enzymes. The presence of alginate gel alters the shape of the active site, reducing activity compared with the free enzyme. Chemically bonding the enzyme is a complex process and is expensive. Any contamination is costly because the whole system has been shutdown and the vessel re sterilized.