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SAJID A Level AQA Biology > 5.1: Defence mechanisms > Flashcards

5.1: Defence mechanisms Flashcards

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1
Q

The immune system

A

The immune system is a system of biological:
1. Structures
2. Processes
within an organism that protects against disease by identifying and killing pathogens (and tumour cells)

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2
Q

Pathogen

A

A pathogen is a disease-causing organism

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3
Q

Infection

A

An infection is an interaction between the:

  1. Pathogen
  2. Body’s various defence mechanisms
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4
Q

Immunity

A

Immunity is when the body’s defence is better prepared for that pathogen

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5
Q

Many pathogens cannot cause disease due to what?

A

Many pathogens cannot cause disease due to:
1. Non-specific barriers
2. Cellular defences
that prevent them from entering the body

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6
Q

Many pathogens cannot cause disease due to non-specific barriers (what barriers) and cellular defences that prevent them from entering the body?

A

Many pathogens cannot cause disease due to:
1. Non-specific barriers (physical and chemical barriers)
2. Cellular defences
that prevent them from entering the body

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7
Q

The main defence mechanisms of the body:

Defence mechanisms are what or what?

A

Defence mechanisms are:
1. Specific
Or,
2. Non-specific

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8
Q

The main defence mechanisms of the body:
Defence mechanisms are specific or non-specific.
With specific defence mechanisms, the response is what?

A

With specific defence mechanisms, the response is:

  1. Slower
  2. Specific to each pathogen
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9
Q

The main defence mechanisms of the body:
Defence mechanisms are specific or non-specific.
With non-specific defence mechanisms, the response is what?

A

With non-specific defence mechanisms, the response is:

  1. Immediate
  2. The same for all pathogens
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10
Q

The main defence mechanisms of the body:
Defence mechanisms are specific or non-specific.
With non-specific defence mechanisms, the response is immediate and the same for all pathogens.
What are the non-specific defence mechanisms of the body?

A

The non-specific defence mechanisms of the body are:

  1. Physical barriers
  2. Phagocytosis
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11
Q

The main defence mechanisms of the body:
Defence mechanisms are specific or non-specific.
With specific defence mechanisms, the response is slower and specific to each pathogen.
What are the specific defence mechanisms of the body?

A

The specific defence mechanisms of the body are the:

  1. Cell-mediated response - T lymphocytes
  2. Humoral response - B lymphocytes
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12
Q

What about when the defence mechanisms of the body fail?
Unfortunately, the defence mechanisms of the body aren’t perfect.
They can and do fail some of the time.
When this happens, what can microorganisms do?

A

When this happens, microorganisms can:

  1. Enter the bloodstream
  2. Cause an infection
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13
Q

An infection is an interaction between the pathogen and the body’s various defence mechanisms.
Sometimes the pathogen does what and the individual dies?

A

Sometimes the pathogen overwhelms the defences and the individual dies

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14
Q

An infection is an interaction between the pathogen and the body’s various defence mechanisms.
Sometimes the pathogen overwhelms the defences and the individual dies.
Sometimes the body’s defence mechanisms do what and the individual recovers from the disease?

A

Sometimes the body’s defence mechanisms overwhelm the pathogen and the individual recovers from the disease

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15
Q

An infection is an interaction between the pathogen and the body’s various defence mechanisms.
Sometimes the pathogen overwhelms the defences and the individual dies.
Sometimes the body’s defence mechanisms overwhelm the pathogen and the individual recovers from the disease.
Having overwhelmed the pathogen, however, the body’s defences seem to be better prepared for a second infection from the same pathogen and can kill it before it can cause any harm.
This is known as immunity and is the main reason why some people are unaffected by certain pathogens.
Much depends on the overall state of health of an individual.
A fit, healthy adult will rarely die to an infection.
Who are usually more vulnerable?

A
  1. Those in ill health
  2. The young
  3. The elderly
    are usually more vulnerable
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16
Q

To defend the body from invasion by foreign material, lymphocytes must be able to do what?

A

To defend the body from invasion by foreign material, lymphocytes must be able to distinguish:
1. The body’s own cells and molecules (self)
from those
2. Molecules that are foreign (non-self)

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17
Q

To defend the body from invasion by foreign material, lymphocytes must be able to distinguish the body’s own cells and molecules (self) from those molecules that are foreign (non-self).
If they could not do this, what would the lymphocytes do?

A

If they could not do this, the lymphocytes would destroy the organism’s own tissues

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18
Q

To defend the body from invasion by foreign material, lymphocytes must be able to distinguish the body’s own cells and molecules (self) from those molecules that are foreign (non-self).
If they could not do this, the lymphocytes would destroy the organism’s own tissues.
Each type of cell, self or non-self, has specific molecules on its surface that do what?

A 
Each type of cell:
1. Self
Or,
2. Non-self
,has specific molecules on its surface that identify it
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19
Q

To defend the body from invasion by foreign material, lymphocytes must be able to distinguish the body’s own cells and molecules (self) from those molecules that are foreign (non-self).
If they could not do this, the lymphocytes would destroy the organism’s own tissues.
Each type of cell, self or non-self, has specific molecules on its surface that identify it.
While these molecules can be of a variety of types, it is the proteins that are the most important.
This is because proteins have enormous variety and what?

A

This is because proteins have:

  1. Enormous variety
  2. A highly specific tertiary structure
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20
Q

To defend the body from invasion by foreign material, lymphocytes must be able to distinguish the body’s own cells and molecules (self) from those molecules that are foreign (non-self).
If they could not do this, the lymphocytes would destroy the organism’s own tissues.
Each type of cell, self or non-self, has specific molecules on its surface that identify it.
While these molecules can be of a variety of types, it is the proteins that are the most important.
This is because proteins have enormous variety and a highly specific tertiary structure.
It is this variety of specific 3D structure that distinguishes one cell from another.
It is these protein molecules which usually allow the immune system to identify what?

A

It is these protein molecules which usually allow the immune system to identify:

  1. Pathogens
  2. Non-self material
  3. Toxins
  4. Abnormal body cells
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21
Q

Each type of cell, self or non-self, has specific molecules on its surface that identify it.
While these molecules can be of a variety of types, it is the proteins that are the most important.
This is because proteins have enormous variety and a highly specific tertiary structure.
It is this variety of specific 3D structure that distinguishes one cell from another.
It is these protein molecules which usually allow the immune system to identify pathogens, for example what, non-self material, toxins and abnormal body cells?

A

It is these protein molecules which usually allow the immune system to identify:

  1. Pathogens, for example the human immunodeficiency virus
  2. Non-self material
  3. Toxins
  4. Abnormal body cells
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22
Q

Each type of cell, self or non-self, has specific molecules on its surface that identify it.
While these molecules can be of a variety of types, it is the proteins that are the most important.
This is because proteins have enormous variety and a highly specific tertiary structure.
It is this variety of specific 3D structure that distinguishes one cell from another.
It is these protein molecules which usually allow the immune system to identify pathogens, for example the human immunodeficiency virus, non-self material, such as what, toxins and abnormal body cells?

A

It is these protein molecules which usually allow the immune system to identify:

  1. Pathogens, for example the human immunodeficiency virus
  2. Non-self material, such as cells from other organisms of the same species
  3. Toxins
  4. Abnormal body cells
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23
Q

Each type of cell, self or non-self, has specific molecules on its surface that identify it.
While these molecules can be of a variety of types, it is the proteins that are the most important.
This is because proteins have enormous variety and a highly specific tertiary structure.
It is this variety of specific 3D structure that distinguishes one cell from another.
It is these protein molecules which usually allow the immune system to identify pathogens, for example the human immunodeficiency virus, non-self material, such as cells from other organisms of the same species, toxins, including those produced by what, and abnormal body cells?

A

It is these protein molecules which usually allow the immune system to identify:

  1. Pathogens, for example the human immunodeficiency virus
  2. Non-self material, such as cells from other organisms of the same species
  3. Toxins, including those produced by certain pathogens like the bacterium that causes cholera
  4. Abnormal body cells
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24
Q

Each type of cell, self or non-self, has specific molecules on its surface that identify it.
While these molecules can be of a variety of types, it is the proteins that are the most important.
This is because proteins have enormous variety and a highly specific tertiary structure.
It is this variety of specific 3D structure that distinguishes one cell from another.
It is these protein molecules which usually allow the immune system to identify pathogens, for example the human immunodeficiency virus, non-self material, such as cells from other organisms of the same species, toxins, including those produced by certain pathogens like the bacterium that causes cholera, and abnormal body cells, such as what?

A

It is these protein molecules which usually allow the immune system to identify:

  1. Pathogens, for example the human immunodeficiency virus
  2. Non-self material, such as cells from other organisms of the same species
  3. Toxins, including those produced by certain pathogens like the bacterium that causes cholera
  4. Abnormal body cells, such as cancer cells
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25
Q

Each type of cell, self or non-self, has specific molecules on its surface that identify it.
While these molecules can be of a variety of types, it is the proteins that are the most important.
This is because proteins have enormous variety and a highly specific tertiary structure.
It is this variety of specific 3D structure that distinguishes one cell from another.
It is these protein molecules which usually allow the immune system to identify pathogens, for example the human immunodeficiency virus, non-self material, such as cells from other organisms of the same species, toxins, including those produced by certain pathogens like the bacterium that causes cholera, and abnormal body cells, such as cancer cells.
All of the above are potentially harmful and their identification is the first stage in removing what?

A

All of the above are potentially harmful and their identification is the first stage in removing the threat they pose

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26
Q

Each type of cell, self or non-self, has specific molecules on its surface that identify it.
While these molecules can be of a variety of types, it is the proteins that are the most important.
This is because proteins have enormous variety and a highly specific tertiary structure.
It is this variety of specific 3D structure that distinguishes one cell from another.
It is these protein molecules which usually allow the immune system to identify pathogens, for example the human immunodeficiency virus, non-self material, such as cells from other organisms of the same species, toxins, including those produced by certain pathogens like the bacterium that causes cholera, and abnormal body cells, such as cancer cells.
All of the above are potentially harmful and their identification is the first stage in removing the threat they pose.
Although this response is clearly advantageous to the organism, it has implications for humans who have had tissue or organ transplants.
The immune system recognises these as non-self, even though they have come from individuals of the same what?

A

The immune system recognises these as non-self, even though they have come from individuals of the same species

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27
Q

It is the protein molecules which usually allow the immune system to identify pathogens, for example the human immunodeficiency virus, non-self material, such as cells from other organisms of the same species, toxins, including those produced by certain pathogens like the bacterium that causes cholera, and abnormal body cells, such as cancer cells.
All of the above are potentially harmful and their identification is the first stage in removing the threat they pose.
Although this response is clearly advantageous to the organism, it has implications for humans who have had tissue or organ transplants.
The immune system recognises these as non-self, even though they have come from individuals of the same species.
The immune system therefore attempts to do what?

A

The immune system therefore attempts to destroy the transplant

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28
Q

It is the protein molecules which usually allow the immune system to identify pathogens, for example the human immunodeficiency virus, non-self material, such as cells from other organisms of the same species, toxins, including those produced by certain pathogens like the bacterium that causes cholera, and abnormal body cells, such as cancer cells.
All of the above are potentially harmful and their identification is the first stage in removing the threat they pose.
Although this response is clearly advantageous to the organism, it has implications for humans who have had tissue or organ transplants.
The immune system recognises these as non-self, even though they have come from individuals of the same species.
The immune system therefore attempts to destroy the transplant.
To minimise the effect of this tissue rejection, donor tissues for transplant are normally what?

A

To minimise the effect of this tissue rejection, donor tissues for transplant are normally matched as closely as possible to those of the recipient

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29
Q

It is the protein molecules which usually allow the immune system to identify pathogens, for example the human immunodeficiency virus, non-self material, such as cells from other organisms of the same species, toxins, including those produced by certain pathogens like the bacterium that causes cholera, and abnormal body cells, such as cancer cells.
All of the above are potentially harmful and their identification is the first stage in removing the threat they pose.
Although this response is clearly advantageous to the organism, it has implications for humans who have had tissue or organ transplants.
The immune system recognises these as non-self, even though they have come from individuals of the same species.
The immune system therefore attempts to destroy the transplant.
To minimise the effect of this tissue rejection, donor tissues for transplant are normally matched as closely as possible to those of the recipient.
The best matches often come from who?

A

The best matches often come from relatives that are genetically close

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30
Q

It is the protein molecules which usually allow the immune system to identify pathogens, for example the human immunodeficiency virus, non-self material, such as cells from other organisms of the same species, toxins, including those produced by certain pathogens like the bacterium that causes cholera, and abnormal body cells, such as cancer cells.
All of the above are potentially harmful and their identification is the first stage in removing the threat they pose.
Although this response is clearly advantageous to the organism, it has implications for humans who have had tissue or organ transplants.
The immune system recognises these as non-self, even though they have come from individuals of the same species.
The immune system therefore attempts to destroy the transplant.
To minimise the effect of this tissue rejection, donor tissues for transplant are normally matched as closely as possible to those of the recipient.
The best matches often come from relatives that are genetically close.
In addition, what are often administered to reduce the level of the immune response that still occurs?

A

In addition, immunosuppressant drugs are often administered to reduce the level of the immune response that still occurs

31
Q

Why are specific lymphocytes not produced in response to an infection?

A

Specific lymphocytes are not produced in response to an infection, because they already exist

32
Q

Specific lymphocytes are not produced in response to an infection, because they already exist - all how many different types?

A

Specific lymphocytes are not produced in response to an infection, because they already exist - all 10 million different types

33
Q

Specific lymphocytes are not produced in response to an infection, because they already exist - all 10 million different types.
Given that there are so many different types of lymphocytes, there is a high probability that, when a pathogen gets into the body, what?

A

Given that there are so many different types of lymphocytes, there is a high probability that, when a pathogen gets into the body, one of these lymphocytes will have a protein on its surface that is complementary to one of the proteins of the pathogen

34
Q

Specific lymphocytes are not produced in response to an infection, because they already exist - all 10 million different types.
Given that there are so many different types of lymphocytes, there is a high probability that, when a pathogen gets into the body, one of these lymphocytes will have a protein on its surface that is complementary to one of the proteins of the pathogen.
The lymphocyte will what?

A

The lymphocyte will ‘recognise’ the pathogen

35
Q

Specific lymphocytes are not produced in response to an infection, because they already exist - all 10 million different types.
Given that there are so many different types of lymphocytes, there is a high probability that, when a pathogen gets into the body, one of these lymphocytes will have a protein on its surface that is complementary to one of the proteins of the pathogen.
The lymphocyte will ‘recognise’ the pathogen.
Not surprisingly with so many different lymphocytes, there are how many of each type?

A

Not surprisingly with so many different lymphocytes, there are very few of each type

36
Q

Specific lymphocytes are not produced in response to an infection, because they already exist - all 10 million different types.
Given that there are so many different types of lymphocytes, there is a high probability that, when a pathogen gets into the body, one of these lymphocytes will have a protein on its surface that is complementary to one of the proteins of the pathogen.
The lymphocyte will ‘recognise’ the pathogen.
Not surprisingly with so many different lymphocytes, there are very few of each type.
When an infection occurs, what happens to the one type of lymphocyte already present that has the complementary proteins to those of the pathogen?

A

When an infection occurs, the one type of lymphocyte already present that has the complementary proteins to those of the pathogen is stimulated to divide to build up its numbers to a level where it can be effective in destroying it

37
Q

Specific lymphocytes are not produced in response to an infection, because they already exist - all 10 million different types.
Given that there are so many different types of lymphocytes, there is a high probability that, when a pathogen gets into the body, one of these lymphocytes will have a protein on its surface that is complementary to one of the proteins of the pathogen.
The lymphocyte will ‘recognise’ the pathogen.
Not surprisingly with so many different lymphocytes, there are very few of each type.
When an infection occurs, the one type of lymphocyte already present that has the complementary proteins to those of the pathogen is stimulated to divide to build up its numbers to a level where it can be effective in destroying it.
This explains why there is a time lag between what?

A

This explains why there is a time lag between:

  1. Exposure to the pathogen
  2. The body’s defences bringing it under control
38
Q

How lymphocytes recognise cells belonging to the body:

1. There are probably around 10 million different lymphocytes present when?

A

There are probably around 10 million different lymphocytes present at any time

39
Q

How lymphocytes recognise cells belonging to the body:

1. There are probably around 10 million different lymphocytes present at any time, each capable of doing what?

A

There are probably around 10 million different lymphocytes present at any time, each capable of recognising a different chemical shape

40
Q

How lymphocytes recognise cells belonging to the body:

  1. There are probably around 10 million different lymphocytes present at any time, each capable of recognising a different chemical shape.
  2. In the fetus, what are these lymphocytes constantly doing?
A

In the fetus, these lymphocytes are constantly colliding with other cells

41
Q

How lymphocytes recognise cells belonging to the body:

  1. There are probably around 10 million different lymphocytes present at any time, each capable of recognising a different chemical shape.
  2. In the fetus, these lymphocytes are constantly colliding with other cells.
  3. Why is infection in the fetus rare?
A

Infection in the fetus is rare, because it is protected from the outside world by:

  1. The mother
  2. In particular, the placenta
42
Q

How lymphocytes recognise cells belonging to the body:

  1. There are probably around 10 million different lymphocytes present at any time, each capable of recognising a different chemical shape.
  2. In the fetus, these lymphocytes are constantly colliding with other cells.
  3. Infection in the fetus is rare, because it is protected from the outside world by the mother and, in particular, the placenta.
  4. What will lymphocytes therefore do?
A

Lymphocytes will therefore collide almost exclusively with the body’s own material (self)

43
Q

How lymphocytes recognise cells belonging to the body:

  1. There are probably around 10 million different lymphocytes present at any time, each capable of recognising a different chemical shape.
  2. In the fetus, these lymphocytes are constantly colliding with other cells.
  3. Infection in the fetus is rare, because it is protected from the outside world by the mother and, in particular, the placenta.
  4. Lymphocytes will therefore collide almost exclusively with the body’s own material (self).
  5. Some of the lymphocytes will have receptors that do what?
A

Some of the lymphocytes will have receptors that exactly fit those of the body’s own cells

44
Q

How lymphocytes recognise cells belonging to the body:
1. There are probably around 10 million different lymphocytes present at any time, each capable of recognising a different chemical shape.
2. In the fetus, these lymphocytes are constantly colliding with other cells.
3. Infection in the fetus is rare, because it is protected from the outside world by the mother and, in particular, the placenta.
4. Lymphocytes will therefore collide almost exclusively with the body’s own material (self).
5. Some of the lymphocytes will have receptors that exactly fit those of the body’s own cells.
What happens to these lymphocytes?

A

These lymphocytes either:
1. Die
Or,
2. Are suppressed

45
Q

How lymphocytes recognise cells belonging to the body:
1. There are probably around 10 million different lymphocytes present at any time, each capable of recognising a different chemical shape.
2. In the fetus, these lymphocytes are constantly colliding with other cells.
3. Infection in the fetus is rare, because it is protected from the outside world by the mother and, in particular, the placenta.
4. Lymphocytes will therefore collide almost exclusively with the body’s own material (self).
5. Some of the lymphocytes will have receptors that exactly fit those of the body’s own cells.
These lymphocytes either die (what) or are suppressed?

A

These lymphocytes either:
1. Die (apoptosis or cell death)
Or,
2. Are suppressed

46
Q

How lymphocytes recognise cells belonging to the body:
1. There are probably around 10 million different lymphocytes present at any time, each capable of recognising a different chemical shape.
2. In the fetus, these lymphocytes are constantly colliding with other cells.
3. Infection in the fetus is rare, because it is protected from the outside world by the mother and, in particular, the placenta.
4. Lymphocytes will therefore collide almost exclusively with the body’s own material (self).
5. Some of the lymphocytes will have receptors that exactly fit those of the body’s own cells.
These lymphocytes either die (apoptosis or cell death) or are suppressed.
6. What are the only remaining lymphocytes?

A

The only remaining lymphocytes are those that might fit foreign material (non-self)

47
Q

How lymphocytes recognise cells belonging to the body:
1. There are probably around 10 million different lymphocytes present at any time, each capable of recognising a different chemical shape.
2. In the fetus, these lymphocytes are constantly colliding with other cells.
3. Infection in the fetus is rare, because it is protected from the outside world by the mother and, in particular, the placenta.
4. Lymphocytes will therefore collide almost exclusively with the body’s own material (self).
5. Some of the lymphocytes will have receptors that exactly fit those of the body’s own cells.
These lymphocytes either die (apoptosis or cell death) or are suppressed.
6. The only remaining lymphocytes are those that might fit foreign material (non-self) and therefore only do what?

A

The only remaining lymphocytes:

  1. Are those that might fit foreign material (non-self)
  2. Therefore only respond to foreign material
48
Q

How lymphocytes recognise cells belonging to the body:
1. There are probably around 10 million different lymphocytes present at any time, each capable of recognising a different chemical shape.
2. In the fetus, these lymphocytes are constantly colliding with other cells.
3. Infection in the fetus is rare, because it is protected from the outside world by the mother and, in particular, the placenta.
4. Lymphocytes will therefore collide almost exclusively with the body’s own material (self).
5. Some of the lymphocytes will have receptors that exactly fit those of the body’s own cells.
These lymphocytes either die (apoptosis or cell death) or are suppressed.
6. The only remaining lymphocytes are those that might fit foreign material (non-self) and therefore only respond to foreign material.
7. In adults, lymphocytes produced in the bone marrow initially only do what?

A

In adults, lymphocytes produced in the bone marrow initially only encounter self-antigens

49
Q

How lymphocytes recognise cells belonging to the body:
1. There are probably around 10 million different lymphocytes present at any time, each capable of recognising a different chemical shape.
2. In the fetus, these lymphocytes are constantly colliding with other cells.
3. Infection in the fetus is rare, because it is protected from the outside world by the mother and, in particular, the placenta.
4. Lymphocytes will therefore collide almost exclusively with the body’s own material (self).
5. Some of the lymphocytes will have receptors that exactly fit those of the body’s own cells.
These lymphocytes either die (apoptosis or cell death) or are suppressed.
6. The only remaining lymphocytes are those that might fit foreign material (non-self) and therefore only respond to foreign material.
7. In adults, lymphocytes produced in the bone marrow initially only encounter self-antigens.
Any lymphocytes that show an immune response to these self-antigens undergo what?

A

Any lymphocytes that show an immune response to these self-antigens undergo programmed cell death (apoptosis)

50
Q

How lymphocytes recognise cells belonging to the body:
1. There are probably around 10 million different lymphocytes present at any time, each capable of recognising a different chemical shape.
2. In the fetus, these lymphocytes are constantly colliding with other cells.
3. Infection in the fetus is rare, because it is protected from the outside world by the mother and, in particular, the placenta.
4. Lymphocytes will therefore collide almost exclusively with the body’s own material (self).
5. Some of the lymphocytes will have receptors that exactly fit those of the body’s own cells.
These lymphocytes either die (apoptosis or cell death) or are suppressed.
6. The only remaining lymphocytes are those that might fit foreign material (non-self) and therefore only respond to foreign material.
7. In adults, lymphocytes produced in the bone marrow initially only encounter self-antigens.
Any lymphocytes that show an immune response to these self-antigens undergo programmed cell death (apoptosis) before they can do what?

A

Any lymphocytes that show an immune response to these self-antigens undergo programmed cell death (apoptosis) before they can differentiate into mature lymphocytes

51
Q

How lymphocytes recognise cells belonging to the body:
1. There are probably around 10 million different lymphocytes present at any time, each capable of recognising a different chemical shape.
2. In the fetus, these lymphocytes are constantly colliding with other cells.
3. Infection in the fetus is rare, because it is protected from the outside world by the mother and, in particular, the placenta.
4. Lymphocytes will therefore collide almost exclusively with the body’s own material (self).
5. Some of the lymphocytes will have receptors that exactly fit those of the body’s own cells.
These lymphocytes either die (apoptosis or cell death) or are suppressed.
6. The only remaining lymphocytes are those that might fit foreign material (non-self) and therefore only respond to foreign material.
7. In adults, lymphocytes produced in the bone marrow initially only encounter self-antigens.
Any lymphocytes that show an immune response to these self-antigens undergo programmed cell death (apoptosis) before they can differentiate into mature lymphocytes.
8. No what will appear in the blood?

A

No clones of these anti-self lymphocytes will appear in the blood

52
Q

How lymphocytes recognise cells belonging to the body:
1. There are probably around 10 million different lymphocytes present at any time, each capable of recognising a different chemical shape.
2. In the fetus, these lymphocytes are constantly colliding with other cells.
3. Infection in the fetus is rare, because it is protected from the outside world by the mother and, in particular, the placenta.
4. Lymphocytes will therefore collide almost exclusively with the body’s own material (self).
5. Some of the lymphocytes will have receptors that exactly fit those of the body’s own cells.
These lymphocytes either die (apoptosis or cell death) or are suppressed.
6. The only remaining lymphocytes are those that might fit foreign material (non-self) and therefore only respond to foreign material.
7. In adults, lymphocytes produced in the bone marrow initially only encounter self-antigens.
Any lymphocytes that show an immune response to these self-antigens undergo programmed cell death (apoptosis) before they can differentiate into mature lymphocytes.
8. No clones of these anti-self lymphocytes will appear in the blood, leaving only what?

A

No clones of these anti-self lymphocytes will appear in the blood, leaving only those that might respond to non-self antigens

53
Q

The first line of defence

A

The first line of defence are the physical barriers

54
Q

The first line of defence are the physical barriers.

What do the physical barriers do?

A

The physical barriers prevent the entry of:
1. Pathogens
2. Microorganisms
only when they are intact

55
Q

The first line of defence are the physical barriers.
The physical barriers prevent the entry of pathogens and microorganisms only when they are intact.
Examples of the types of physical barriers

A

Examples of the types of physical barriers are:

  1. Skin
  2. Tears
  3. Eyelashes
  4. Mucus
  5. Ciliated cells
56
Q

The first line of defence are the physical barriers.
Skin:
The skin is an organ.
The skin is a what barrier to infection?

A

The skin is a huge barrier to infection

57
Q 
The first line of defence are the physical barriers.
Skin:
The skin is an organ.
The skin is a huge barrier to infection.
What secrete sebum?
A

Sebaceous glands in the dermis secrete sebum

58
Q

The first line of defence are the physical barriers.
Skin:
The skin is an organ.
The skin is a huge barrier to infection.
Sebaceous glands in the dermis secrete sebum, a what substance?

A

Sebaceous glands in the dermis secrete sebum, an oily substance

59
Q

The first line of defence are the physical barriers.
Skin:
The skin is an organ.
The skin is a huge barrier to infection.
Sebaceous glands in the dermis secrete sebum, an oily substance, that helps to keep skin what?

A

Sebaceous glands in the dermis secrete sebum, an oily substance, that helps to keep skin pliable

60
Q

The first line of defence are the physical barriers.
Skin:
The skin is an organ.
The skin is a huge barrier to infection.
Sebaceous glands in the dermis secrete sebum, an oily substance, that helps to keep skin pliable, but it is also what?

A

Sebaceous glands in the dermis secrete sebum, an oily substance, that helps to keep skin pliable, but it is also acidic

61
Q

The first line of defence are the physical barriers.
Skin:
The skin is an organ.
The skin is a huge barrier to infection.
Sebaceous glands in the dermis secrete sebum, an oily substance, that helps to keep skin pliable, but it is also acidic and so what does it do?

A

Sebaceous glands in the dermis secrete sebum, an oily substance, that helps to keep skin pliable, but it:

  1. Is also acidic
  2. So lowers the pH of the skin
62
Q

The first line of defence are the physical barriers.
Skin:
The skin is an organ.
The skin is a huge barrier to infection.
Sebaceous glands in the dermis secrete sebum, an oily substance, that helps to keep skin pliable, but it is also acidic and so lowers the pH of the skin, thus inhibiting what?

A

Sebaceous glands in the dermis secrete sebum, an oily substance, that helps to keep skin pliable, but it:
1. Is also acidic
2. So lowers the pH of the skin
,thus inhibiting the growth of some types of bacteria

63
Q

The first line of defence are the physical barriers.
Skin:
The skin is an organ.
The skin is a huge barrier to infection.
Sebaceous glands in the dermis secrete sebum, an oily substance, that helps to keep skin pliable, but it is also acidic and so lowers the pH of the skin, thus inhibiting the growth of some types of bacteria.
Sweat is also a defence mechanism that contains what?

A

Sweat is also a defence mechanism that contains:

  1. Salts
  2. Enzymes
64
Q

The first line of defence are the physical barriers.
Skin:
The skin is an organ.
The skin is a huge barrier to infection.
Sebaceous glands in the dermis secrete sebum, an oily substance, that helps to keep skin pliable, but it is also acidic and so lowers the pH of the skin, thus inhibiting the growth of some types of bacteria.
Sweat is also a defence mechanism that contains salts and enzymes, which make it difficult for bacteria to do what and make it difficult for certain types of bacteria to do what?

A

Sweat is also a defence mechanism that contains salts and enzymes, which make it difficult for:

  1. Bacteria to inhabit the skin’s surface
  2. Certain types of bacteria to survive
65
Q

The first line of defence are the physical barriers.
Tears:
What do tears contain?

A

Tears contain lysozymes

66
Q

The first line of defence are the physical barriers.
Tears:
Tears contain lysozymes that are enzymes that can do what?

A

Tears contain lysozymes that are enzymes that can destroy bacterial cells

67
Q

The first line of defence are the physical barriers.
Tears:
Tears contain lysozymes that are enzymes that can destroy bacterial cells.
What does this do?

A

This prevents the entry of pathogens in the eyes

68
Q

The first line of defence are the physical barriers.
Eyelashes:
What do eyelashes do?

A

Eyelashes respond to foreign bodies near the eyes

69
Q

The first line of defence are the physical barriers.
Eyelashes:
Eyelashes respond to foreign bodies near the eyes by what?

A

Eyelashes respond to foreign bodies near the eyes by blinking

70
Q

The first line of defence are the physical barriers.
The digestive system:
The stomach contains hydrochloric acid that lowers what?

A

The stomach contains hydrochloric acid that lowers its pH

71
Q

The first line of defence are the physical barriers.
The digestive system:
The stomach contains hydrochloric acid that lowers its pH to what?

A

The stomach contains hydrochloric acid that lowers its pH to between:
1. 1.5
2. 2.5
pH

72
Q

The first line of defence are the physical barriers.
The digestive system:
The stomach contains hydrochloric acid that lowers its pH to between 1.5 and 2.5 pH.
What does this mean?

A

This means that it is an inhospitable environment for bacteria to survive

73
Q

What do cilia do?

A

Cilia sweep away trapped particles

74
Q

What does mucus do?

A

Mucus traps foreign bodies

SAJID A Level AQA Biology (69 decks)

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