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1

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

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

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?

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

3

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

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

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?

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

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?

The 2 changes most frequently measured are the:
1. Formation of the products of the reaction
2. Disappearance of the substrate

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?

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

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?

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

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?

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

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?

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

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?

All enzyme active sites are filled at any given moment

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?

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

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?

The amount of substrate decreases as it is broken down

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?

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

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?

As the reaction proceeds, there is:
1. Less and less substrate
2. More and more product

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?

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

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?

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

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?

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

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?

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

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?

Consequently, the rate of formation of product also slows

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?

Both graphs 'tail off'

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?

The rate of reaction continues to slow

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?

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

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?

The graphs flatten out

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?

The graphs flatten out, because:
1. All the substrate has been used up
2. So no new product can be produced

25

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

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

26

Rate is always expressed how?

Rate is always expressed per unit time

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?

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

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?

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

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?

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

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'?

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

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?

The correct term is complementary

32

The effect of temperature on enzyme action:
A rise in temperature does what?

A rise in temperature increases the kinetic energy of molecules

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?

As a result, the molecules:
1. Move around more rapidly
2. Collide with each other more often

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?

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

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?

There are more effective collisions

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?

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

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?

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

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?

Shown on a graph, this gives a rising curve

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?

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

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?

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

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?

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

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?

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

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?

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

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?

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

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?

The enzyme is said to be denatured

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?

Denaturation is a permanent change

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?

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

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?

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

49

The effect of temperature on enzyme action:
The optimum working temperature differs from what?

The optimum working temperature differs from enzyme to enzyme

50

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

Some work fastest at around 10 degrees Celsius

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?

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

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?

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

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?

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

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?

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

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?

Although higher body temperatures would increase the metabolic rate slightly

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?

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

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?

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

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?

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

59

The effect of temperature on enzyme action:
Different species of what have different what?

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

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?

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

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?

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

62

The effect of pH on enzyme action:
What is the pH of a solution?

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

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?

Each enzyme has an optimum pH

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?

This is a pH at which it works the fastest

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?

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

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?

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

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?

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

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?

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

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?

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

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?

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

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?

The active site therefore changes shape

72

The effect of pH on enzyme action:
The arrangement of the active site is partly determined by what?

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

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?

The change in H+ ions affects this bonding

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?

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

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?

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

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?

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

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?

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

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?

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

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?

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

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?

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

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?

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

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?

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

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?

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

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?

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

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?

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

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?

The rate of reaction will therefore stabilise at a constant level

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?

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

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?

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

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?

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

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?

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

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?

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

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?

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

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?

The rate of reaction has doubled to its maximum

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?

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

95

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

The addition of further enzyme molecules has no effect

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?

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

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?

There is no increase in the rate of reaction

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?

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

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?

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

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?

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

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?

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

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?

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

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?

The rate of reaction is at its maximum

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?

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

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?

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

106

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

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

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?

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

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?

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

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?

The rate of reaction has doubled to its maximum

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?

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

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?

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

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?

There is no increase in the rate of reaction

113

The effect of temperature on enzyme action:
If the temperature goes above a certain level, what break?

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

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?

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

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?

The active site of the enzyme changes shape

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?

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

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?

The enzyme is denatured

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?

No successful collisions leads to a low rate of reaction

119

The effect of pH on enzyme action:
Just like temperature, we have an optimum pH level, which is what?

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

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?

Pepsin works best at pH 2

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?

This will happen until a 'saturation' point

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?

This will happen until a 'saturation' point, where:
1. All the enzymes are used
2. Adding more substrate will make no difference

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?

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