1.8: The factors affecting enzyme action

Question 1

Before considering how pH and temperature affect enzymes, it is worth bearing in mind that for an enzyme to work, it must what?

Answer 1

Before considering how pH and temperature affect enzymes, it is worth bearing in mind that for an enzyme to work, it must:

1. Come into physical contact with its substrate
2. Have an active site that fits the substrate

Question 2

Before considering how pH and temperature affect enzymes, it is worth bearing in mind that for an enzyme to work, it must come into physical contact with its substrate and have an active site that fits the substrate.
Almost all factors that influence the rate at which an enzyme works do so by affecting one or both of the above.
In order to investigate how enzymes are affected by various factors, we need to be able to do what?

Answer 2

In order to investigate how enzymes are affected by various factors, we need to be able to measure the rate of the reactions they catalyse

Question 3

Measuring enzyme-catalysed reactions:

To measure the progress of an enzyme-catalysed reaction, we usually do what?

Answer 3

To measure the progress of an enzyme-catalysed reaction, we usually measure its time-course

Question 4

Measuring enzyme-catalysed reactions:
To measure the progress of an enzyme-catalysed reaction, we usually measure its time-course, that is how long it takes for what?

Answer 4

To measure the progress of an enzyme-catalysed reaction, we usually measure its time-course, that is how long it takes for a particular event to run its course

Question 5

Measuring enzyme-catalysed reactions:
To measure the progress of an enzyme-catalysed reaction, we usually measure its time-course, that is how long it takes for a particular event to run its course.
The how many changes most frequently measured are what?

Answer 5

The 2 changes most frequently measured are the:

1. Formation of the products of the reaction
2. Disappearance of the substrate

Question 6

Measuring enzyme-catalysed reactions:
To measure the progress of an enzyme-catalysed reaction, we usually measure its time-course, that is how long it takes for a particular event to run its course.
The 2 changes most frequently measured are the formation of the products of the reaction, for example what, and the disappearance of the substrate?

Answer 6

The 2 changes most frequently measured are the:

1. Formation of the products of the reaction, for example the volume of oxygen produced when the enzyme catalase acts on hydrogen peroxide
2. Disappearance of the substrate

Question 7

Measuring enzyme-catalysed reactions:
To measure the progress of an enzyme-catalysed reaction, we usually measure its time-course, that is how long it takes for a particular event to run its course.
The 2 changes most frequently measured are the formation of the products of the reaction, for example the volume of oxygen produced when the enzyme catalase acts on hydrogen peroxide, and the disappearance of the substrate, for example what?

Answer 7

The 2 changes most frequently measured are the:

1. Formation of the products of the reaction, for example the volume of oxygen produced when the enzyme catalase acts on hydrogen peroxide
2. Disappearance of the substrate, for example the reduction in concentration of starch when it is acted upon by amylase

Question 8

One graph showing a curve from the bottom going up to the top right and another graph showing a curve from the top to the bottom right.
Although the graphs differ, the explanation for the shapes is the same:
At first, there is what?

Answer 8

At first there is:
1. A lot of substrate
,but
2. No product

Question 9

One graph showing a curve from the bottom going up to the top right and another graph showing a curve from the top to the bottom right.
Although the graphs differ, the explanation for the shapes is the same:
At first, there is a lot of substrate, but no product.
It is very easy for substrate molecules to do what?

Answer 9

It is very easy for substrate molecules to come into contact with the empty active sites on the enzyme molecules

Question 10

One graph showing a curve from the bottom going up to the top right and another graph showing a curve from the top to the bottom right.
Although the graphs differ, the explanation for the shapes is the same:
At first, there is a lot of substrate, but no product.
It is very easy for substrate molecules to come into contact with the empty active sites on the enzyme molecules.
All enzyme active sites are what at any given moment?

Answer 10

All enzyme active sites are filled at any given moment

Question 11

One graph showing a curve from the bottom going up to the top right and another graph showing a curve from the top to the bottom right.
Although the graphs differ, the explanation for the shapes is the same:
At first, there is a lot of substrate, but no product.
It is very easy for substrate molecules to come into contact with the empty active sites on the enzyme molecules.
All enzyme active sites are filled at any given moment and the substrate is what?

Answer 11

All enzyme active sites are filled at any given moment and the substrate is rapidly broken down into its products

Question 12

One graph showing a curve from the bottom going up to the top right and another graph showing a curve from the top to the bottom right.
Although the graphs differ, the explanation for the shapes is the same:
At first, there is a lot of substrate, but no product.
It is very easy for substrate molecules to come into contact with the empty active sites on the enzyme molecules.
All enzyme active sites are filled at any given moment and the substrate is rapidly broken down into its products.
The amount of substrate does what as it is broken down?

Answer 12

The amount of substrate decreases as it is broken down

Question 13

One graph showing a curve from the bottom going up to the top right and another graph showing a curve from the top to the bottom right.
Although the graphs differ, the explanation for the shapes is the same:
At first, there is a lot of substrate, but no product.
It is very easy for substrate molecules to come into contact with the empty active sites on the enzyme molecules.
All enzyme active sites are filled at any given moment and the substrate is rapidly broken down into its products.
The amount of substrate decreases as it is broken down, resulting in what?

Answer 13

The amount of substrate decreases as it is broken down, resulting in an increase in the amount of product

Question 14

One graph showing a curve from the bottom going up to the top right and another graph showing a curve from the top to the bottom right.
Although the graphs differ, the explanation for the shapes is the same:
At first, there is a lot of substrate, but no product.
It is very easy for substrate molecules to come into contact with the empty active sites on the enzyme molecules.
All enzyme active sites are filled at any given moment and the substrate is rapidly broken down into its products.
The amount of substrate decreases as it is broken down, resulting in an increase in the amount of product.
As the reaction proceeds, there is what?

Answer 14

As the reaction proceeds, there is:

1. Less and less substrate
2. More and more product

Question 15

One graph showing a curve from the bottom going up to the top right and another graph showing a curve from the top to the bottom right.
Although the graphs differ, the explanation for the shapes is the same:
At first, there is a lot of substrate, but no product.
It is very easy for substrate molecules to come into contact with the empty active sites on the enzyme molecules.
All enzyme active sites are filled at any given moment and the substrate is rapidly broken down into its products.
The amount of substrate decreases as it is broken down, resulting in an increase in the amount of product.
As the reaction proceeds, there is less and less substrate and more and more product.
It becomes what for the substrate molecules to do what?

Answer 15

It becomes difficult for the substrate molecules to come into contact with the enzyme molecules

Question 16

One graph showing a curve from the bottom going up to the top right and another graph showing a curve from the top to the bottom right.
Although the graphs differ, the explanation for the shapes is the same:
At first, there is a lot of substrate, but no product.
It is very easy for substrate molecules to come into contact with the empty active sites on the enzyme molecules.
All enzyme active sites are filled at any given moment and the substrate is rapidly broken down into its products.
The amount of substrate decreases as it is broken down, resulting in an increase in the amount of product.
As the reaction proceeds, there is less and less substrate and more and more product.
Why does it become difficult for the substrate molecules to come into contact with the enzyme molecules?

Answer 16

It becomes difficult for the substrate molecules to come into contact with the enzyme molecules, because:

1. There are fewer substrate molecules
2. Also the product molecules may ‘get in the way’ of substrate molecules and prevent them from reaching an active site

Question 17

One graph showing a curve from the bottom going up to the top right and another graph showing a curve from the top to the bottom right.
Although the graphs differ, the explanation for the shapes is the same:
At first, there is a lot of substrate, but no product.
It is very easy for substrate molecules to come into contact with the empty active sites on the enzyme molecules.
All enzyme active sites are filled at any given moment and the substrate is rapidly broken down into its products.
The amount of substrate decreases as it is broken down, resulting in an increase in the amount of product.
As the reaction proceeds, there is less and less substrate and more and more product.
It becomes difficult for the substrate molecules to come into contact with the enzyme molecules, because there are fewer substrate molecules and also the product molecules may ‘get in the way’ of substrate molecules and prevent them from reaching an active site.
It therefore takes longer for what?

Answer 17

It therefore takes longer for the substrate molecules to be broken down by the enzyme

Question 18

One graph showing a curve from the bottom going up to the top right and another graph showing a curve from the top to the bottom right.
Although the graphs differ, the explanation for the shapes is the same:
At first, there is a lot of substrate, but no product.
It is very easy for substrate molecules to come into contact with the empty active sites on the enzyme molecules.
All enzyme active sites are filled at any given moment and the substrate is rapidly broken down into its products.
The amount of substrate decreases as it is broken down, resulting in an increase in the amount of product.
As the reaction proceeds, there is less and less substrate and more and more product.
It becomes difficult for the substrate molecules to come into contact with the enzyme molecules, because there are fewer substrate molecules and also the product molecules may ‘get in the way’ of substrate molecules and prevent them from reaching an active site.
It therefore takes longer for the substrate molecules to be broken down by the enzyme and so what slows?

Answer 18

It therefore:

1. Takes longer for the substrate molecules to be broken down by the enzyme
2. So its rate of disappearance slows

Question 19

One graph showing a curve from the bottom going up to the top right and another graph showing a curve from the top to the bottom right.
Although the graphs differ, the explanation for the shapes is the same:
At first, there is a lot of substrate, but no product.
It is very easy for substrate molecules to come into contact with the empty active sites on the enzyme molecules.
All enzyme active sites are filled at any given moment and the substrate is rapidly broken down into its products.
The amount of substrate decreases as it is broken down, resulting in an increase in the amount of product.
As the reaction proceeds, there is less and less substrate and more and more product.
It becomes difficult for the substrate molecules to come into contact with the enzyme molecules, because there are fewer substrate molecules and also the product molecules may ‘get in the way’ of substrate molecules and prevent them from reaching an active site.
It therefore takes longer for the substrate molecules to be broken down by the enzyme and so its rate of disappearance slows.
Consequently, what also slows?

Answer 19

Consequently, the rate of formation of product also slows

Question 20

One graph showing a curve from the bottom going up to the top right and another graph showing a curve from the top to the bottom right.
Although the graphs differ, the explanation for the shapes is the same:
At first, there is a lot of substrate, but no product.
It is very easy for substrate molecules to come into contact with the empty active sites on the enzyme molecules.
All enzyme active sites are filled at any given moment and the substrate is rapidly broken down into its products.
The amount of substrate decreases as it is broken down, resulting in an increase in the amount of product.
As the reaction proceeds, there is less and less substrate and more and more product.
It becomes difficult for the substrate molecules to come into contact with the enzyme molecules, because there are fewer substrate molecules and also the product molecules may ‘get in the way’ of substrate molecules and prevent them from reaching an active site.
It therefore takes longer for the substrate molecules to be broken down by the enzyme and so its rate of disappearance slows.
Consequently, the rate of formation of product also slows.
Both graphs do what?

Answer 20

Both graphs ‘tail off’

Question 21

One graph showing a curve from the bottom going up to the top right and another graph showing a curve from the top to the bottom right.
Although the graphs differ, the explanation for the shapes is the same:
At first, there is a lot of substrate, but no product.
It is very easy for substrate molecules to come into contact with the empty active sites on the enzyme molecules.
All enzyme active sites are filled at any given moment and the substrate is rapidly broken down into its products.
The amount of substrate decreases as it is broken down, resulting in an increase in the amount of product.
As the reaction proceeds, there is less and less substrate and more and more product.
It becomes difficult for the substrate molecules to come into contact with the enzyme molecules, because there are fewer substrate molecules and also the product molecules may ‘get in the way’ of substrate molecules and prevent them from reaching an active site.
It therefore takes longer for the substrate molecules to be broken down by the enzyme and so its rate of disappearance slows.
Consequently, the rate of formation of product also slows.
Both graphs ‘tail off.’
The rate of reaction continues to do what?

Answer 21

The rate of reaction continues to slow

Question 22

One graph showing a curve from the bottom going up to the top right and another graph showing a curve from the top to the bottom right.
Although the graphs differ, the explanation for the shapes is the same:
At first, there is a lot of substrate, but no product.
It is very easy for substrate molecules to come into contact with the empty active sites on the enzyme molecules.
All enzyme active sites are filled at any given moment and the substrate is rapidly broken down into its products.
The amount of substrate decreases as it is broken down, resulting in an increase in the amount of product.
As the reaction proceeds, there is less and less substrate and more and more product.
It becomes difficult for the substrate molecules to come into contact with the enzyme molecules, because there are fewer substrate molecules and also the product molecules may ‘get in the way’ of substrate molecules and prevent them from reaching an active site.
It therefore takes longer for the substrate molecules to be broken down by the enzyme and so its rate of disappearance slows.
Consequently, the rate of formation of product also slows.
Both graphs ‘tail off.’
The rate of reaction continues to slow until what?

Answer 22

The rate of reaction continues to slow until there is so little substrate that any further decrease in its concentration cannot be measured

Question 23

One graph showing a curve from the bottom going up to the top right and another graph showing a curve from the top to the bottom right.
Although the graphs differ, the explanation for the shapes is the same:
At first, there is a lot of substrate, but no product.
It is very easy for substrate molecules to come into contact with the empty active sites on the enzyme molecules.
All enzyme active sites are filled at any given moment and the substrate is rapidly broken down into its products.
The amount of substrate decreases as it is broken down, resulting in an increase in the amount of product.
As the reaction proceeds, there is less and less substrate and more and more product.
It becomes difficult for the substrate molecules to come into contact with the enzyme molecules, because there are fewer substrate molecules and also the product molecules may ‘get in the way’ of substrate molecules and prevent them from reaching an active site.
It therefore takes longer for the substrate molecules to be broken down by the enzyme and so its rate of disappearance slows.
Consequently, the rate of formation of product also slows.
Both graphs ‘tail off.’
The rate of reaction continues to slow until there is so little substrate that any further decrease in its concentration cannot be measured.
The graphs do what?

Answer 23

The graphs flatten out

Question 24

One graph showing a curve from the bottom going up to the top right and another graph showing a curve from the top to the bottom right.
Although the graphs differ, the explanation for the shapes is the same:
At first, there is a lot of substrate, but no product.
It is very easy for substrate molecules to come into contact with the empty active sites on the enzyme molecules.
All enzyme active sites are filled at any given moment and the substrate is rapidly broken down into its products.
The amount of substrate decreases as it is broken down, resulting in an increase in the amount of product.
As the reaction proceeds, there is less and less substrate and more and more product.
It becomes difficult for the substrate molecules to come into contact with the enzyme molecules, because there are fewer substrate molecules and also the product molecules may ‘get in the way’ of substrate molecules and prevent them from reaching an active site.
It therefore takes longer for the substrate molecules to be broken down by the enzyme and so its rate of disappearance slows.
Consequently, the rate of formation of product also slows.
Both graphs ‘tail off.’
The rate of reaction continues to slow until there is so little substrate that any further decrease in its concentration cannot be measured.
Why do the graphs flatten out?

Answer 24

The graphs flatten out, because:

1. All the substrate has been used up
2. So no new product can be produced

Question 25

We can measure the change in the rate of a reaction at any point on the curve of a graph by doing what?

Answer 25

We can measure the change in the rate of a reaction at any point on the curve of a graph by measuring the gradient at our chosen point

Question 26

Rate is always expressed how?

Answer 26

Rate is always expressed per unit time

Question 27

Before we look at the effects of different factors on the rate of enzyme action, it is important to stress the fundamental experimental technique of changing only a single variable in each experiment.
When investigating the effect of a named variable on the rate of an enzyme reaction, all the other variables must be what?

Answer 27

When investigating the effect of a named variable on the rate of an enzyme reaction, all the other variables must be kept constant

Question 28

Before we look at the effects of different factors on the rate of enzyme action, it is important to stress the fundamental experimental technique of changing only a single variable in each experiment.
When investigating the effect of a named variable on the rate of an enzyme reaction, all the other variables must be kept constant.
For example, if measuring the effect of temperature, then what must be kept constant?

Answer 28

For example, if measuring the effect of temperature, then:
1. pH
2. Enzyme concentration
3. Substrate concentration
must be kept constant

Question 29

Before we look at the effects of different factors on the rate of enzyme action, it is important to stress the fundamental experimental technique of changing only a single variable in each experiment.
When investigating the effect of a named variable on the rate of an enzyme reaction, all the other variables must be kept constant.
For example, if measuring the effect of temperature, then pH, enzyme concentration and substrate concentration must be kept constant and what?

Answer 29

For example, if measuring the effect of temperature, then:

1. pH, enzyme concentration and substrate concentration must be kept constant
2. All possible inhibitors should be absent

Question 30

Before we look at the effects of different factors on the rate of enzyme action, it is important to stress the fundamental experimental technique of changing only a single variable in each experiment.
When investigating the effect of a named variable on the rate of an enzyme reaction, all the other variables must be kept constant.
For example, if measuring the effect of temperature, then pH, enzyme concentration and substrate concentration must be kept constant and all possible inhibitors should be absent.
Another thing to remember is the what are not ‘the same’?

Answer 30

Another thing to remember is that the:
1. Active site
2. Substrate
are not ‘the same’

Question 31

Before we look at the effects of different factors on the rate of enzyme action, it is important to stress the fundamental experimental technique of changing only a single variable in each experiment.
When investigating the effect of a named variable on the rate of an enzyme reaction, all the other variables must be kept constant.
For example, if measuring the effect of temperature, then pH, enzyme concentration and substrate concentration must be kept constant and all possible inhibitors should be absent.
Another thing to remember is the active site and the substrate are not ‘the same.’
The correct term is what?

Answer 31

The correct term is complementary

Question 32

The effect of temperature on enzyme action:

A rise in temperature does what?

Answer 32

A rise in temperature increases the kinetic energy of molecules

Question 33

The effect of temperature on enzyme action:
A rise in temperature increases the kinetic energy of molecules.
As a result, the molecules do what?

Answer 33

As a result, the molecules:

1. Move around more rapidly
2. Collide with each other more often

Question 34

The effect of temperature on enzyme action:
A rise in temperature increases the kinetic energy of molecules.
As a result, the molecules move around more rapidly and collide with each other more often.
In an enzyme-catalysed reaction, what does this mean?

Answer 34

In an enzyme-catalysed reaction, this means that the:
1. Enzyme
2. Substrate
molecules come together more often in a given time

Question 35

The effect of temperature on enzyme action:
A rise in temperature increases the kinetic energy of molecules.
As a result, the molecules move around more rapidly and collide with each other more often.
In an enzyme-catalysed reaction, this means that the enzyme and substrate molecules come together more often in a given time.
There are more what?

Answer 35

There are more effective collisions

Question 36

The effect of temperature on enzyme action:
A rise in temperature increases the kinetic energy of molecules.
As a result, the molecules move around more rapidly and collide with each other more often.
In an enzyme-catalysed reaction, this means that the enzyme and substrate molecules come together more often in a given time.
There are more effective collisions, resulting in what?

Answer 36

There are more effective collisions, resulting in more enzyme-substrate complexes being formed

Question 37

The effect of temperature on enzyme action:
A rise in temperature increases the kinetic energy of molecules.
As a result, the molecules move around more rapidly and collide with each other more often.
In an enzyme-catalysed reaction, this means that the enzyme and substrate molecules come together more often in a given time.
There are more effective collisions, resulting in more enzyme-substrate complexes being formed and so what?

Answer 37

There are more effective collisions, resulting in more enzyme-substrate complexes being formed and so the rate of reaction increases

Question 38

The effect of temperature on enzyme action:
A rise in temperature increases the kinetic energy of molecules.
As a result, the molecules move around more rapidly and collide with each other more often.
In an enzyme-catalysed reaction, this means that the enzyme and substrate molecules come together more often in a given time.
There are more effective collisions, resulting in more enzyme-substrate complexes being formed and so the rate of reaction increases.
Shown on a graph, this gives what?

Answer 38

Shown on a graph, this gives a rising curve

Question 39

The effect of temperature on enzyme action:
A rise in temperature increases the kinetic energy of molecules.
As a result, the molecules move around more rapidly and collide with each other more often.
In an enzyme-catalysed reaction, this means that the enzyme and substrate molecules come together more often in a given time.
There are more effective collisions, resulting in more enzyme-substrate complexes being formed and so the rate of reaction increases.
Shown on a graph, this gives a rising curve.
However, the temperature rise also does what?

Answer 39

The temperature rise also begins to cause:
1. The hydrogen bonds
2. Other bonds in the enzyme molecule
to break

Question 40

The effect of temperature on enzyme action:
A rise in temperature increases the kinetic energy of molecules.
As a result, the molecules move around more rapidly and collide with each other more often.
In an enzyme-catalysed reaction, this means that the enzyme and substrate molecules come together more often in a given time.
There are more effective collisions, resulting in more enzyme-substrate complexes being formed and so the rate of reaction increases.
Shown on a graph, this gives a rising curve.
However, the temperature rise also begins to cause the hydrogen bonds and other bonds in the enzyme molecule to break.
This results in what?

Answer 40

This results in the enzyme, including its active site, changing shape

Question 41

The effect of temperature on enzyme action:
A rise in temperature increases the kinetic energy of molecules.
As a result, the molecules move around more rapidly and collide with each other more often.
In an enzyme-catalysed reaction, this means that the enzyme and substrate molecules come together more often in a given time.
There are more effective collisions, resulting in more enzyme-substrate complexes being formed and so the rate of reaction increases.
Shown on a graph, this gives a rising curve.
However, the temperature rise also begins to cause the hydrogen bonds and other bonds in the enzyme molecule to break.
This results in the enzyme, including its active site, changing shape.
At first, what happens?

Answer 41

At first, the substrate fits less easily into this changed active site

Question 42

The effect of temperature on enzyme action:
A rise in temperature increases the kinetic energy of molecules.
As a result, the molecules move around more rapidly and collide with each other more often.
In an enzyme-catalysed reaction, this means that the enzyme and substrate molecules come together more often in a given time.
There are more effective collisions, resulting in more enzyme-substrate complexes being formed and so the rate of reaction increases.
Shown on a graph, this gives a rising curve.
However, the temperature rise also begins to cause the hydrogen bonds and other bonds in the enzyme molecule to break.
This results in the enzyme, including its active site, changing shape.
At first, the substrate fits less easily into this changed active site, doing what?

Answer 42

At first, the substrate fits less easily into this changed active site, slowing the rate of reaction

Question 43

The effect of temperature on enzyme action:
A rise in temperature increases the kinetic energy of molecules.
As a result, the molecules move around more rapidly and collide with each other more often.
In an enzyme-catalysed reaction, this means that the enzyme and substrate molecules come together more often in a given time.
There are more effective collisions, resulting in more enzyme-substrate complexes being formed and so the rate of reaction increases.
Shown on a graph, this gives a rising curve.
However, the temperature rise also begins to cause the hydrogen bonds and other bonds in the enzyme molecule to break.
This results in the enzyme, including its active site, changing shape.
At first, the substrate fits less easily into this changed active site, slowing the rate of reaction.
For many what enzymes, this may begin at temperatures of what?

Answer 43

For many human enzymes, this may begin at temperatures of around 45 degrees Celsius

Question 44

The effect of temperature on enzyme action:
A rise in temperature increases the kinetic energy of molecules.
As a result, the molecules move around more rapidly and collide with each other more often.
In an enzyme-catalysed reaction, this means that the enzyme and substrate molecules come together more often in a given time.
There are more effective collisions, resulting in more enzyme-substrate complexes being formed and so the rate of reaction increases.
Shown on a graph, this gives a rising curve.
However, the temperature rise also begins to cause the hydrogen bonds and other bonds in the enzyme molecule to break.
This results in the enzyme, including its active site, changing shape.
At first, the substrate fits less easily into this changed active site, slowing the rate of reaction.
For many human enzymes, this may begin at temperatures of around 45 degrees Celsius.
At some point, usually around what temperature, what happens?

Answer 44

At some point, usually around 60 degrees Celsius, the enzyme is so disrupted that it stops working altogether

Question 45

The effect of temperature on enzyme action:
A rise in temperature increases the kinetic energy of molecules.
As a result, the molecules move around more rapidly and collide with each other more often.
In an enzyme-catalysed reaction, this means that the enzyme and substrate molecules come together more often in a given time.
There are more effective collisions, resulting in more enzyme-substrate complexes being formed and so the rate of reaction increases.
Shown on a graph, this gives a rising curve.
However, the temperature rise also begins to cause the hydrogen bonds and other bonds in the enzyme molecule to break.
This results in the enzyme, including its active site, changing shape.
At first, the substrate fits less easily into this changed active site, slowing the rate of reaction.
For many human enzymes, this may begin at temperatures of around 45 degrees Celsius.
At some point, usually around 60 degrees Celsius, the enzyme is so disrupted that it stops working altogether.
It is said to be what?

Answer 45

The enzyme is said to be denatured

Question 46

The effect of temperature on enzyme action:
A rise in temperature increases the kinetic energy of molecules.
As a result, the molecules move around more rapidly and collide with each other more often.
In an enzyme-catalysed reaction, this means that the enzyme and substrate molecules come together more often in a given time.
There are more effective collisions, resulting in more enzyme-substrate complexes being formed and so the rate of reaction increases.
Shown on a graph, this gives a rising curve.
However, the temperature rise also begins to cause the hydrogen bonds and other bonds in the enzyme molecule to break.
This results in the enzyme, including its active site, changing shape.
At first, the substrate fits less easily into this changed active site, slowing the rate of reaction.
For many human enzymes, this may begin at temperatures of around 45 degrees Celsius.
At some point, usually around 60 degrees Celsius, the enzyme is so disrupted that it stops working altogether.
The enzyme is said to be denatured.
Denaturation is a what change?

Answer 46

Denaturation is a permanent change

Question 47

The effect of temperature on enzyme action:
A rise in temperature increases the kinetic energy of molecules.
As a result, the molecules move around more rapidly and collide with each other more often.
In an enzyme-catalysed reaction, this means that the enzyme and substrate molecules come together more often in a given time.
There are more effective collisions, resulting in more enzyme-substrate complexes being formed and so the rate of reaction increases.
Shown on a graph, this gives a rising curve.
However, the temperature rise also begins to cause the hydrogen bonds and other bonds in the enzyme molecule to break.
This results in the enzyme, including its active site, changing shape.
At first, the substrate fits less easily into this changed active site, slowing the rate of reaction.
For many human enzymes, this may begin at temperatures of around 45 degrees Celsius.
At some point, usually around 60 degrees Celsius, the enzyme is so disrupted that it stops working altogether.
The enzyme is said to be denatured.
Denaturation is a permanent change and, once it has occurred, the enzyme does not what?

Answer 47

Denaturation is a permanent change and, once it has occurred, the enzyme does not function again

Question 48

The effect of temperature on enzyme action:
A rise in temperature increases the kinetic energy of molecules.
As a result, the molecules move around more rapidly and collide with each other more often.
In an enzyme-catalysed reaction, this means that the enzyme and substrate molecules come together more often in a given time.
There are more effective collisions, resulting in more enzyme-substrate complexes being formed and so the rate of reaction increases.
Shown on a graph, this gives a rising curve.
However, the temperature rise also begins to cause the hydrogen bonds and other bonds in the enzyme molecule to break.
This results in the enzyme, including its active site, changing shape.
At first, the substrate fits less easily into this changed active site, slowing the rate of reaction.
For many human enzymes, this may begin at temperatures of around 45 degrees Celsius.
At some point, usually around 60 degrees Celsius, the enzyme is so disrupted that it stops working altogether.
The enzyme is said to be denatured.
Denaturation is a permanent change and, once it has occurred, the enzyme does not function again.
Shown on a graph, the rate of reaction follows what?

Answer 48

Shown on a graph, the rate of reaction follows a falling curve

Question 49

The effect of temperature on enzyme action:

The optimum working temperature differs from what?

Answer 49

The optimum working temperature differs from enzyme to enzyme

Question 50

The effect of temperature on enzyme action:
The optimum working temperature differs from enzyme to enzyme.
Some work fastest at around what temperature?

Answer 50

Some work fastest at around 10 degrees Celsius

Question 51

The effect of temperature on enzyme action:
The optimum working temperature differs from enzyme to enzyme.
Some work fastest at around 10 degrees Celsius, while others continue to work rapidly at what temperature?

Answer 51

Some work fastest at around 10 degrees Celsius, while others continue to work rapidly at 80 degrees Celsius

Question 52

The effect of temperature on enzyme action:
The optimum working temperature differs from enzyme to enzyme.
Some work fastest at around 10 degrees Celsius, while others continue to work rapidly at 80 degrees Celsius, for example what?

Answer 52

Some work fastest at around 10 degrees Celsius, while others continue to work rapidly at 80 degrees Celsius, for example enzymes used in:

1. Biological washing powders
2. The polymerase chain reaction

Question 53

The effect of temperature on enzyme action:
The optimum working temperature differs from enzyme to enzyme.
Some work fastest at around 10 degrees Celsius, while others continue to work rapidly at 80 degrees Celsius, for example enzymes used in biological washing powders and in the polymerase chain reaction.
Many enzymes in the human body have an optimum temperature of what?

Answer 53

Many enzymes in the human body have an optimum temperature of about 40 degrees Celsius

Question 54

The effect of temperature on enzyme action:
The optimum working temperature differs from enzyme to enzyme.
Some work fastest at around 10 degrees Celsius, while others continue to work rapidly at 80 degrees Celsius, for example enzymes used in biological washing powders and in the polymerase chain reaction.
Many enzymes in the human body have an optimum temperature of about 40 degrees Celsius.
Our body temperatures have, however, evolved to be what?

Answer 54

Our body temperatures have, however, evolved to be 37 degrees Celsius

Question 55

The effect of temperature on enzyme action:
Many enzymes in the human body have an optimum temperature of about 40 degrees Celsius.
Our body temperatures have, however, evolved to be 37 degrees Celsius.
This may be related to the following:
1. Although higher body temperatures would increase the what slightly?

Answer 55

Although higher body temperatures would increase the metabolic rate slightly

Question 56

The effect of temperature on enzyme action:
Many enzymes in the human body have an optimum temperature of about 40 degrees Celsius.
Our body temperatures have, however, evolved to be 37 degrees Celsius.
This may be related to the following:
1. Although higher body temperatures would increase the metabolic rate slightly, the advantages are offset by what?

Answer 56

Although higher body temperatures would increase the metabolic rate slightly, the advantages are offset by the additional energy (food) that would be needed to maintain the higher temperature

Question 57

The effect of temperature on enzyme action:
Many enzymes in the human body have an optimum temperature of about 40 degrees Celsius.
Our body temperatures have, however, evolved to be 37 degrees Celsius.
This may be related to the following:
1. Although higher body temperatures would increase the metabolic rate slightly, the advantages are offset by the additional energy (food) that would be needed to maintain the higher temperature.
2. Other what, apart from enzymes, may be denatured at higher temperatures?

Answer 57

Other proteins, apart from enzymes, may be denatured at higher temperatures

Question 58

The effect of temperature on enzyme action:
Many enzymes in the human body have an optimum temperature of about 40 degrees Celsius.
Our body temperatures have, however, evolved to be 37 degrees Celsius.
This may be related to the following:
1. Although higher body temperatures would increase the metabolic rate slightly, the advantages are offset by the additional energy (food) that would be needed to maintain the higher temperature.
2. Other proteins, apart from enzymes, may be denatured at higher temperatures.
3. At higher temperatures, any further rise in temperature, for example when, might do what?

Answer 58

At higher temperatures, any further rise in temperature, for example during illness, might denature the enzymes

Question 59

The effect of temperature on enzyme action:

Different species of what have different what?

Answer 59

Different species of:
1. Mammals
2. Birds
have different body temperatures

Question 60

The effect of temperature on enzyme action:
Different species of mammals and birds have different body temperatures.
Many birds, for example, have a normal body temperature of what?

Answer 60

Many birds, for example, have a normal body temperature of around 40 degrees Celsius

Question 61

The effect of temperature on enzyme action:
Different species of mammals and birds have different body temperatures.
Many birds, for example, have a normal body temperature of around 40 degrees Celsius, because they have what for what?

Answer 61

Many birds, for example, have a normal body temperature of around 40 degrees Celsius, because they have a high metabolic rate for the high energy requirement of flight

Question 62

The effect of pH on enzyme action:

What is the pH of a solution?

Answer 62

The pH of a solution is a measure of its hydrogen ion concentration

Question 63

The effect of pH on enzyme action:
The pH of a solution is a measure of its hydrogen ion concentration.
Each enzyme has a what?

Answer 63

Each enzyme has an optimum pH

Question 64

The effect of pH on enzyme action:
The pH of a solution is a measure of its hydrogen ion concentration.
Each enzyme has an optimum pH.
This is a pH at which it what?

Answer 64

This is a pH at which it works the fastest

Question 65

The effect of pH on enzyme action:
The pH of a solution is a measure of its hydrogen ion concentration.
Each enzyme has an optimum pH.
This is a pH at which it works the fasted.
An increase or decrease in pH does what?

Answer 65

An:
1. Increase
Or,
2. Decrease
in pH reduces the rate of enzyme action

Question 66

The effect of pH on enzyme action:
The pH of a solution is a measure of its hydrogen ion concentration.
Each enzyme has an optimum pH.
This is a pH at which it works the fasted.
An increase or decrease in pH reduces the rate of enzyme action.
If the change in pH is more extreme, then, beyond a certain pH, the enzyme does what?

Answer 66

If the change in pH is more extreme, then, beyond a certain pH, the enzyme becomes denatured

Question 67

The effect of pH on enzyme action:
The pH affects how an enzyme works in the following ways:
1. A change in pH alters what?

Answer 67

A change in pH alters the charges on the amino acids that make up the active site of the enzyme

Question 68

The effect of pH on enzyme action:
The pH affects how an enzyme works in the following ways:
1. A change in pH alters the charges on the amino acids that make up the active site of the enzyme.
As a result, the substrate can no longer do what?

Answer 68

As a result, the substrate can no longer become attached to the active site

Question 69

The effect of pH on enzyme action:
The pH affects how an enzyme works in the following ways:
1. A change in pH alters the charges on the amino acids that make up the active site of the enzyme.
As a result, the substrate can no longer become attached to the active site and so what cannot be formed?

Answer 69

As a result:

1. The substrate can no longer become attached to the active site
2. So the enzyme-substrate complex cannot be formed

Question 70

The effect of pH on enzyme action:
The pH affects how an enzyme works in the following ways:
1. A change in pH alters the charges on the amino acids that make up the active site of the enzyme.
As a result, the substrate can no longer become attached to the active site and so the enzyme-substrate complex cannot be formed.
2. Depending on how what the change in pH is, it may do what?

Answer 70

Depending on how significant the change in pH is, it may cause the bonds maintaining the enzyme’s tertiary structure to break

Question 71

The effect of pH on enzyme action:
The pH affects how an enzyme works in the following ways:
1. A change in pH alters the charges on the amino acids that make up the active site of the enzyme.
As a result, the substrate can no longer become attached to the active site and so the enzyme-substrate complex cannot be formed.
2. Depending on how significant the change in pH is, it may cause the bonds maintaining the enzyme’s tertiary structure to break.
What therefore changes shape?

Answer 71

The active site therefore changes shape

Question 72

The effect of pH on enzyme action:

The arrangement of the active site is partly determined by what?

Answer 72

The arrangement of the active site is partly determined by the:
1. Hydrogen
2. Ionic
bonds between the -NH2 and -COOH groups of the polypeptides that make up the enzyme

Question 73

The effect of pH on enzyme action:
The pH of a solution is a measure of its hydrogen ion concentration.
The arrangement of the active site is partly determined by the hydrogen and ionic bonds between the -NH2 and -COOH groups of the polypeptides that make up the enzyme.
The change in what affects this bonding?

Answer 73

The change in H+ ions affects this bonding

Question 74

The effect of pH on enzyme action:
The pH of a solution is a measure of its hydrogen ion concentration.
The arrangement of the active site is partly determined by the hydrogen and ionic bonds between the -NH2 and -COOH groups of the polypeptides that make up the enzyme.
The change in H+ ions affects this bonding, causing what?

Answer 74

The change in H+ ions affects this bonding, causing the active site to change shape

Question 75

The effect of pH on enzyme action:
The pH of a solution is a measure of its hydrogen ion concentration.
The arrangement of the active site is partly determined by the hydrogen and ionic bonds between the -NH2 and -COOH groups of the polypeptides that make up the enzyme.
The change in H+ ions affects this bonding, causing the active site to change shape.
It is important to note that pH fluctuations inside organisms are usually what?

Answer 75

It is important to note that pH fluctuations inside organisms are usually small

Question 76

The effect of pH on enzyme action:
The pH of a solution is a measure of its hydrogen ion concentration.
The arrangement of the active site is partly determined by the hydrogen and ionic bonds between the -NH2 and -COOH groups of the polypeptides that make up the enzyme.
The change in H+ ions affects this bonding, causing the active site to change shape.
It is important to note that pH fluctuations inside organisms are usually small.
This means they are far more likely to do what than what?

Answer 76

This means they are far more likely to:
1. Reduce an enzyme’s activity
than
2. Denature it

Question 77

The effect of enzyme concentration on the rate of reaction:

Once an active site on an enzyme has acted on its substrate, it is free to do what?

Answer 77

Once an active site on an enzyme has acted on its substrate, it is free to repeat the procedure on another substrate molecule

Question 78

The effect of enzyme concentration on the rate of reaction:
Once an active site on an enzyme has acted on its substrate, it is free to repeat the procedure on another substrate molecule.
This means that enzymes, being what, are not what?

Answer 78

This means that enzymes, being catalysts, are not used up in the reaction

Question 79

The effect of enzyme concentration on the rate of reaction:
Once an active site on an enzyme has acted on its substrate, it is free to repeat the procedure on another substrate molecule.
This means that enzymes, being catalysts, are not used up in the reaction and therefore what?

Answer 79

This means that enzymes, being catalysts, are not used up in the reaction and therefore work efficiently at very low concentrations

Question 80

The effect of enzyme concentration on the rate of reaction:
Once an active site on an enzyme has acted on its substrate, it is free to repeat the procedure on another substrate molecule.
This means that enzymes, being catalysts, are not used up in the reaction and therefore work efficiently at very low concentrations.
In some cases, a single enzyme molecule can do what in one minute?

Answer 80

In some cases, a single enzyme molecule can act on millions of substrate molecules in one minute

Question 81

The effect of enzyme concentration on the rate of reaction:
Once an active site on an enzyme has acted on its substrate, it is free to repeat the procedure on another substrate molecule.
This means that enzymes, being catalysts, are not used up in the reaction and therefore work efficiently at very low concentrations.
In some cases, a single enzyme molecule can act on millions of substrate molecules in one minute.
As long as there is an excess of substrate, an increase in the amount of enzyme leads to a what?

Answer 81

As long as there is an excess of substrate, an increase in the amount of enzyme leads to a proportionate increase in the rate of reaction

Question 82

The effect of enzyme concentration on the rate of reaction:
Once an active site on an enzyme has acted on its substrate, it is free to repeat the procedure on another substrate molecule.
This means that enzymes, being catalysts, are not used up in the reaction and therefore work efficiently at very low concentrations.
In some cases, a single enzyme molecule can act on millions of substrate molecules in one minute.
As long as there is an excess of substrate, an increase in the amount of enzyme leads to a proportionate increase in the rate of reaction.
A graph of the rate of reaction against enzyme concentration will initially show what?

Answer 82

A graph of the rate of reaction against enzyme concentration will initially show a proportionate increase

Question 83

The effect of enzyme concentration on the rate of reaction:
Once an active site on an enzyme has acted on its substrate, it is free to repeat the procedure on another substrate molecule.
This means that enzymes, being catalysts, are not used up in the reaction and therefore work efficiently at very low concentrations.
In some cases, a single enzyme molecule can act on millions of substrate molecules in one minute.
As long as there is an excess of substrate, an increase in the amount of enzyme leads to a proportionate increase in the rate of reaction.
A graph of the rate of reaction against enzyme concentration will initially show a proportionate increase.
This is because there is what?

Answer 83

This is because there is more substrate than the enzyme’s active sites can cope with

Question 84

The effect of enzyme concentration on the rate of reaction:
Once an active site on an enzyme has acted on its substrate, it is free to repeat the procedure on another substrate molecule.
This means that enzymes, being catalysts, are not used up in the reaction and therefore work efficiently at very low concentrations.
In some cases, a single enzyme molecule can act on millions of substrate molecules in one minute.
As long as there is an excess of substrate, an increase in the amount of enzyme leads to a proportionate increase in the rate of reaction.
A graph of the rate of reaction against enzyme concentration will initially show a proportionate increase.
This is because there is more substrate than the enzyme’s active sites can cope with.
If you therefore increase the enzyme concentration, what happens?

Answer 84

If you therefore increase the enzyme concentration:

1. Some of the excess substrate can now also be acted upon
2. The rate of reaction will increase

Question 85

The effect of enzyme concentration on the rate of reaction:
Once an active site on an enzyme has acted on its substrate, it is free to repeat the procedure on another substrate molecule.
This means that enzymes, being catalysts, are not used up in the reaction and therefore work efficiently at very low concentrations.
In some cases, a single enzyme molecule can act on millions of substrate molecules in one minute.
As long as there is an excess of substrate, an increase in the amount of enzyme leads to a proportionate increase in the rate of reaction.
A graph of the rate of reaction against enzyme concentration will initially show a proportionate increase.
This is because there is more substrate than the enzyme’s active sites can cope with.
If you therefore increase the enzyme concentration, some of the excess substrate can now also be acted upon and the rate of reaction will increase.
If, however, the substrate is limiting (there is not sufficient to supply all the enzyme’s active sites at one time, then any increase in enzyme concentration will have what effect on the rate of reaction?

Answer 85

If, however, the substrate is limiting (there is not sufficient to supply all the enzyme’s active sites at one time, then any increase in enzyme concentration will have no effect on the rate of reaction

Question 86

The effect of enzyme concentration on the rate of reaction:
Once an active site on an enzyme has acted on its substrate, it is free to repeat the procedure on another substrate molecule.
This means that enzymes, being catalysts, are not used up in the reaction and therefore work efficiently at very low concentrations.
In some cases, a single enzyme molecule can act on millions of substrate molecules in one minute.
As long as there is an excess of substrate, an increase in the amount of enzyme leads to a proportionate increase in the rate of reaction.
A graph of the rate of reaction against enzyme concentration will initially show a proportionate increase.
This is because there is more substrate than the enzyme’s active sites can cope with.
If you therefore increase the enzyme concentration, some of the excess substrate can now also be acted upon and the rate of reaction will increase.
If, however, the substrate is limiting (there is not sufficient to supply all the enzyme’s active sites at one time, then any increase in enzyme concentration will have no effect on the rate of reaction.
The rate of reaction will therefore do what?

Answer 86

The rate of reaction will therefore stabilise at a constant level

Question 87

The effect of enzyme concentration on the rate of reaction:
Once an active site on an enzyme has acted on its substrate, it is free to repeat the procedure on another substrate molecule.
This means that enzymes, being catalysts, are not used up in the reaction and therefore work efficiently at very low concentrations.
In some cases, a single enzyme molecule can act on millions of substrate molecules in one minute.
As long as there is an excess of substrate, an increase in the amount of enzyme leads to a proportionate increase in the rate of reaction.
A graph of the rate of reaction against enzyme concentration will initially show a proportionate increase.
This is because there is more substrate than the enzyme’s active sites can cope with.
If you therefore increase the enzyme concentration, some of the excess substrate can now also be acted upon and the rate of reaction will increase.
If, however, the substrate is limiting (there is not sufficient to supply all the enzyme’s active sites at one time, then any increase in enzyme concentration will have no effect on the rate of reaction.
The rate of reaction will therefore stabilise at a constant level, meaning the graph will do what?

Answer 87

The rate of reaction will therefore stabilise at a constant level, meaning the graph will level off

Question 88

The effect of enzyme concentration on the rate of reaction:
Once an active site on an enzyme has acted on its substrate, it is free to repeat the procedure on another substrate molecule.
This means that enzymes, being catalysts, are not used up in the reaction and therefore work efficiently at very low concentrations.
In some cases, a single enzyme molecule can act on millions of substrate molecules in one minute.
As long as there is an excess of substrate, an increase in the amount of enzyme leads to a proportionate increase in the rate of reaction.
A graph of the rate of reaction against enzyme concentration will initially show a proportionate increase.
This is because there is more substrate than the enzyme’s active sites can cope with.
If you therefore increase the enzyme concentration, some of the excess substrate can now also be acted upon and the rate of reaction will increase.
If, however, the substrate is limiting (there is not sufficient to supply all the enzyme’s active sites at one time, then any increase in enzyme concentration will have no effect on the rate of reaction.
The rate of reaction will therefore stabilise at a constant level, meaning the graph will level off.
This is because the available substrate is already what?

Answer 88

This is because the available substrate is already being used as rapidly as it can be

Question 89

The effect of enzyme concentration on the rate of reaction:
Once an active site on an enzyme has acted on its substrate, it is free to repeat the procedure on another substrate molecule.
This means that enzymes, being catalysts, are not used up in the reaction and therefore work efficiently at very low concentrations.
In some cases, a single enzyme molecule can act on millions of substrate molecules in one minute.
As long as there is an excess of substrate, an increase in the amount of enzyme leads to a proportionate increase in the rate of reaction.
A graph of the rate of reaction against enzyme concentration will initially show a proportionate increase.
This is because there is more substrate than the enzyme’s active sites can cope with.
If you therefore increase the enzyme concentration, some of the excess substrate can now also be acted upon and the rate of reaction will increase.
If, however, the substrate is limiting (there is not sufficient to supply all the enzyme’s active sites at one time, then any increase in enzyme concentration will have no effect on the rate of reaction.
The rate of reaction will therefore stabilise at a constant level, meaning the graph will level off.
This is because the available substrate is already being used as rapidly as it can be by what?

Answer 89

This is because the available substrate is already being used as rapidly as it can be by the existing enzyme molecules

Question 90

The effect of enzyme concentration on the rate of reaction:
Low enzyme concentration:
There are too few what molecules to allow all substrate molecules to do what?

Answer 90

There are too few enzyme molecules to allow all substrate molecules to find an active site at one time

Question 91

The effect of enzyme concentration on the rate of reaction:
Low enzyme concentration:
There are too few enzyme molecules to allow all substrate molecules to find an active site at one time.
The rate of reaction is therefore only what?

Answer 91

The rate of reaction is therefore only half the maximum possible for the number of substrate molecules available

Question 92

The effect of enzyme concentration on the rate of reaction:
Intermediate enzyme concentration:
With twice as many enzyme molecules available, all the substrate molecules can do what?

Answer 92

With twice as many enzyme molecules available, all the substrate molecules can occupy an active site at the same time

Question 93

The effect of enzyme concentration on the rate of reaction:
Intermediate enzyme concentration:
With twice as many enzyme molecules available, all the substrate molecules can occupy an active site at the same time.
The rate of reaction has what to its maximum?

Answer 93

The rate of reaction has doubled to its maximum

Question 94

The effect of enzyme concentration on the rate of reaction:
Intermediate enzyme concentration:
With twice as many enzyme molecules available, all the substrate molecules can occupy an active site at the same time.
The rate of reaction has doubled to its maximum, because what?

Answer 94

The rate of reaction has doubled to its maximum, because all the active sites are filled

Question 95

The effect of enzyme concentration on the rate of reaction:
High enzyme concentration:
The addition of further enzyme molecules has what?

Answer 95

The addition of further enzyme molecules has no effect

Question 96

The effect of enzyme concentration on the rate of reaction:
High enzyme concentration:
The addition of further enzyme molecules has no effect, because there are already what to do what?

Answer 96

The addition of further enzyme molecules has no effect, because there are already enough active sites to accommodate all the available substrate molecules

Question 97

The effect of enzyme concentration on the rate of reaction:
High enzyme concentration:
The addition of further enzyme molecules has no effect, because there are already enough active sites to accommodate all the available substrate molecules.
There is no what in the rate of reaction?

Answer 97

There is no increase in the rate of reaction

Question 98

The effects of substrate concentration on the rate of enzyme action:
If the concentration of enzyme is what and the substrate concentration is slowly what, the rate of reaction increases how?

Answer 98

If the:
1. Concentration of enzyme is fixed
2. Substrate concentration is slowly increased
,the rate of reaction increases in proportion to the concentration of substrate

Question 99

The effects of substrate concentration on the rate of enzyme action:
If the concentration of enzyme is fixed and the substrate concentration is slowly increased, the rate of reaction increases in proportion to the concentration of substrate.
This is because at low substrate concentrations, the enzyme molecules have only what to collide with?

Answer 99

This is because at low substrate concentrations, the enzyme molecules have only a limited number of substrate molecules to collide with

Question 100

The effects of substrate concentration on the rate of enzyme action:
If the concentration of enzyme is fixed and the substrate concentration is slowly increased, the rate of reaction increases in proportion to the concentration of substrate.
This is because at low substrate concentrations, the enzyme molecules have only a limited number of substrate molecules to collide with and therefore what?

Answer 100

This is because at low substrate concentrations:

1. The enzyme molecules have only a limited number of substrate molecules to collide with
2. Therefore the active sites of the enzymes are not working to full capacity

Question 101

The effects of substrate concentration on the rate of enzyme action:
If the concentration of enzyme is fixed and the substrate concentration is slowly increased, the rate of reaction increases in proportion to the concentration of substrate.
This is because at low substrate concentrations, the enzyme molecules have only a limited number of substrate molecules to collide with and therefore the active sites of the enzymes are not working to full capacity.
As more substrate is added, the active sites what?

Answer 101

As more substrate is added, the active sites gradually become filled

Question 102

The effects of substrate concentration on the rate of enzyme action:
If the concentration of enzyme is fixed and the substrate concentration is slowly increased, the rate of reaction increases in proportion to the concentration of substrate.
This is because at low substrate concentrations, the enzyme molecules have only a limited number of substrate molecules to collide with and therefore the active sites of the enzymes are not working to full capacity.
As more substrate is added, the active sites gradually become filled, until what?

Answer 102

As more substrate is added, the active sites gradually become filled, until the point where all of them are working as fast as they can

Question 103

The effects of substrate concentration on the rate of enzyme action:
If the concentration of enzyme is fixed and the substrate concentration is slowly increased, the rate of reaction increases in proportion to the concentration of substrate.
This is because at low substrate concentrations, the enzyme molecules have only a limited number of substrate molecules to collide with and therefore the active sites of the enzymes are not working to full capacity.
As more substrate is added, the active sites gradually become filled, until the point where all of them are working as fast as they can.
The rate of reaction is at its what?

Answer 103

The rate of reaction is at its maximum

Question 104

The effects of substrate concentration on the rate of enzyme action:
If the concentration of enzyme is fixed and the substrate concentration is slowly increased, the rate of reaction increases in proportion to the concentration of substrate.
This is because at low substrate concentrations, the enzyme molecules have only a limited number of substrate molecules to collide with and therefore the active sites of the enzymes are not working to full capacity.
As more substrate is added, the active sites gradually become filled, until the point where all of them are working as fast as they can.
The rate of reaction is at its maximum.
After that, the addition of more substrate will have what effect on the rate of reaction?

Answer 104

After that, the addition of more substrate will have no effect on the rate of reaction

Question 105

The effects of substrate concentration on the rate of enzyme action:
If the concentration of enzyme is fixed and the substrate concentration is slowly increased, the rate of reaction increases in proportion to the concentration of substrate.
This is because at low substrate concentrations, the enzyme molecules have only a limited number of substrate molecules to collide with and therefore the active sites of the enzymes are not working to full capacity.
As more substrate is added, the active sites gradually become filled, until the point where all of them are working as fast as they can.
The rate of reaction is at its maximum.
After that, the addition of more substrate will have no effect on the rate of reaction.
When there is an excess of substrate, the rate of reaction does what?

Answer 105

When there is an excess of substrate, the rate of reaction levels off

Question 106

The effects of substrate concentration on the rate of enzyme action:
Low substrate concentration:
There are too few substrate molecules to do what?

Answer 106

There are too few substrate molecules to occupy all the available active sites

Question 107

The effects of substrate concentration on the rate of enzyme action:
Low substrate concentration:
There are too few substrate molecules to occupy all the available active sites.
The rate of reaction is therefore only what the maximum possible for what?

Answer 107

The rate of reaction is therefore only half the maximum possible for the number of enzyme molecules available

Question 108

The effects of substrate concentration on the rate of enzyme action:
Intermediate substrate concentration:
With how many substrate molecules available, all the active sites are occupied when?

Answer 108

With twice as many substrate molecules available, all the active sites are occupied at one time

Question 109

The effects of substrate concentration on the rate of enzyme action:
Intermediate substrate concentration:
With twice as many substrate molecules available, all the active sites are occupied at one time.
The rate of reaction has what to its maximum?

Answer 109

The rate of reaction has doubled to its maximum

Question 110

The effects of substrate concentration on the rate of enzyme action:
Intermediate substrate concentration:
With twice as many substrate molecules available, all the active sites are occupied at one time.
Why has the rate of reaction doubled to its maximum?

Answer 110

The rate of reaction has doubled to its maximum, because all the active sites are filled

Question 111

The effects of substrate concentration on the rate of enzyme action:
High substrate concentration:
The addition of further substrate molecules has no effect, because what?

Answer 111

The addition of further substrate molecules has no effect, because all the active sites are already occupied at one time

Question 112

The effects of substrate concentration on the rate of enzyme action:
High substrate concentration:
The addition of further substrate molecules has no effect, because all the active sites are already occupied at one time.
There is no what in the rate of reaction?

Answer 112

There is no increase in the rate of reaction

Question 113

The effect of temperature on enzyme action:

If the temperature goes above a certain level, what break?

Answer 113

If the temperature goes above a certain level, the bonds holding the tertiary (3D) structure of the enzyme break

Question 114

The effect of temperature on enzyme action:
If the temperature goes above a certain level, the bonds holding the tertiary (3D) structure of the enzyme break, so what does the enzyme do?

Answer 114

If the temperature goes above a certain level, the bonds holding the tertiary (3D) structure of the enzyme break, so the enzyme loses its shape

Question 115

The effect of temperature on enzyme action:
If the temperature goes above a certain level, the bonds holding the tertiary (3D) structure of the enzyme break, so the enzyme loses its shape.
What changes shape?

Answer 115

The active site of the enzyme changes shape

Question 116

The effect of temperature on enzyme action:
If the temperature goes above a certain level, the bonds holding the tertiary (3D) structure of the enzyme break, so the enzyme loses its shape.
The active site of the enzyme changes shape, so what?

Answer 116

The active site of the enzyme changes shape, so the substrate no longer fits

Question 117

The effect of temperature on enzyme action:
If the temperature goes above a certain level, the bonds holding the tertiary (3D) structure of the enzyme are broken, so the enzyme loses its shape.
The active site of the enzyme changes shape, so the substrate no longer fits.
The enzyme is what?

Answer 117

The enzyme is denatured

Question 118

The effect of temperature on enzyme action:
If the temperature goes above a certain level, the bonds holding the tertiary (3D) structure of the enzyme break, so the enzyme loses its shape.
The active site of the enzyme changes shape, so the substrate no longer fits.
The enzyme is denatured.
No what leads to a low rate of reaction?

Answer 118

No successful collisions leads to a low rate of reaction

Question 119

The effect of pH on enzyme action:

Just like temperature, we have an optimum pH level, which is what?

Answer 119

Just like temperature, we have an optimum pH level, which is pH 7

Question 120

The effect of pH on enzyme action:
Just like temperature, we have an optimum pH level, which is pH 7.
However, what works best at pH 2?

Answer 120

Pepsin works best at pH 2

Question 121

The effects of substrate concentration on the rate of enzyme action:
An increase in substrate concentration means greater collisions between the substrates and enzymes.
This will happen until when?

Answer 121

This will happen until a ‘saturation’ point

Question 122

The effects of substrate concentration on the rate of enzyme action:
An increase in substrate concentration means greater collisions between the substrates and enzymes.
This will happen until a ‘saturation’ point, where what?

Answer 122

This will happen until a ‘saturation’ point, where:

1. All the enzymes are used
2. Adding more substrate will make no difference

Question 123

The effects of substrate concentration on the rate of enzyme action:
At the beginning, the rate of reaction is low when there is a low substrate concentration, because few substrate molecules do what?

Answer 123

At the beginning, the rate of reaction is low when there is a low substrate concentration, because few substrate molecules limit the chance of successful collisions between the:

1. Enzyme
2. Substrate