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Biology > 3.2.4 - Cells - Cell recognition and the immune system > Flashcards

3.2.4 - Cells - Cell recognition and the immune system Flashcards

1
Q

which cells identify the presence of pathogens and potentially harmful foreign substances in the body and to destroy or neutralise them to prevent harm?

A

lymphocytes

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2
Q

what are antigens made from?

A

proteins

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3
Q

what do different surface molecules enable them to identify?

A

pathogens (e.g. bacteria, fungi or viruses such as HIV)

cells from other organisms of the same species (harmful for those with organ transplants)

abnormal body cells (e.g. cancer cells)

toxins

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4
Q

what can each different shape lymphocyte do?

A

each one can recognise a different shaped antigen

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5
Q

when are lymphocytes made?

A

when you are a foetus

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6
Q

what is the definition of an antigen?

A

foreign proteins that generate an immune response by lymphocyte cells when detected in the body

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7
Q

where are antigens located?

A

on the surface of cells

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8
Q

what happens if a mutation occurs in the gene which codes for the antigen?

A

the shape of the antigen will change

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9
Q

what happens to the previous immunity to a pathogen if there is a mutation of the antigens?

A

any previous immunity to this pathogen (either naturally
through prior infection or artificially through vaccination) is
no longer effective, as all the memory cells in the blood will
have a memory of the old antigen shape

this is antigen variability

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10
Q

what is an example of a chemical barrier that pathogens have to get past?

A

stomach acid

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11
Q

what is an example of a physical barrier that pathogens have to get past?

A

skin

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12
Q

what line of defence are the white blood cells?

A

if the pathogen enters the blood then the white blood cells are the second line of defence

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13
Q

what type of white blood cells are responsible for the non-specific response?

A

phagocytes

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14
Q

what type of white blood cells are responsible for the specific response?

A

lymphocytes

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15
Q

what type of white blood cell is a phagocyte?

A

macrophage

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16
Q

where are phagocytes found?

A

found in the blood and in tissues

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17
Q

is phagocytosis a specific or non-specific response?

A

a non-specific response

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18
Q

what is the process of phagocytosis?

A

phagocytes are in the blood and tissues and any chemicals
or debris released by pathogens or abnormal cells attract
the phagocytes and they will move towards these cells

there are many receptor binding points on the surface of phagocytes, they will attach to chemicals or antigens on the pathogen via these receptors

the phagocyte changes shape to move around and engulf the pathogen, once engulfed, the pathogen is contained with a phagosome vesicle

a lysosome within the phagocyte will fuse with the phagosome and release its contents, the lysozyme enzyme is released into the phagosome

this is a lytic enzyme which hydrolyses the pathogen, this destroys the pathogen, the soluble products are absorbed and used by the phagocyte

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19
Q

where are all lymphocytes made?

A

made in the bone marrow

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20
Q

where do T cells mature?

A

in the thymus

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21
Q

which cells does the cell-mediated response involve?

A

T cells and body cells

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22
Q

how is the cell mediated response specific?

A

because T cells respond to antigens on the surface of cells

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23
Q

what are Antigen-Presenting Cells (APC)?

A

any cell that presents a non-self antigen on their surface

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24
Q

what are examples of APC?

A

infected body cells presenting viral antigens on their surface

a macrophage which has engulfed and destroyed a pathogen presenting the antigens on their surface

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25
Q

why is cell mediated response described as ‘cell-mediated’?

A

because T cells only respond to antigens which are presented on cells (APC), and not antigens detached from cells and within body fluids, such as the blood

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26
Q

what is the process of cell mediated response?

A

1 - once a pathogen has been engulfed and destroyed by a phagocyte, the antigens are positioned on the cell surface, this is now called an antigen-presenting cell (APC)

2 - helper T cells have receptors on their surface which can attach to the antigens on APC

3 - once attached this activates the helper T cells to divide by mitosis to replicate and make large numbers of clones, cloned helper T cells differentiate into different cells

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27
Q

what are the different cells that cloned helper T cells differentiate into during cell mediated response?

A

some remain as helper T cells and activate B lymphocytes

some stimulate macrophages to perform more phagocytosis

some become memory cells for that shaped antigen

some become cytotoxic T cells (killer T cells)

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28
Q

what do cytotoxic T cells do?

A

destroy abnormal or infected cells

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29
Q

how do cytotoxic cells destroy abnormal or infected cells?

A

they release a protein, perforin, which embeds in the cell surface
membrane and makes a pore (a hole) so that any substances
can enter or leave the cell and this causes cell death

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30
Q

when are cytotoxic T cells most common?

A

in viral infections because viruses infect body cells, body cells are sacrificed to prevent viral replication

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31
Q

where do B cells mature?

A

in the bone marrow

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32
Q

what does the humoral response involve?

A

the response involving B cells and antibodies

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33
Q

how are antibodies transported around the body and are they soluble?

A

antibodies are soluble and transported in bodily fluids

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34
Q

what happens in the process of B cell activation?

A

antigens in the blood collide with their complementary antibody on a B cell

the B cell takes in the antigen by endocytosis and then presents it on its cell surface membrane

when this B cell collides with a helper T cell receptor, this activates the B cell to go through clonal expansion and differentiation (clonal selection)

B cells undergo mitosis to make large numbers of cells, these differentiate into plasma cells or memory B cells

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35
Q

do plasma cells make antibodies?

A

yes

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36
Q

how do B memory cells make antibodies?

A

divide rapidly into plasma cells when reinfected with the same pathogen to make large numbers of antibodies rapidly

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37
Q

how long can memory B cells live for in your body?

A

decades

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38
Q

how long do plasma cells live for?

A

short lived

39
Q

what do memory B cells do instead of making antibodies?

A

they will divide by mitosis and make plasma cells rapidly if they collide with an antigen they have previously encountered

40
Q

what is active immunity?

A

where large numbers of antibodies being produced so rapidly that the pathogen is destroyed before any symptoms can occur

41
Q

what is the definition of an antibody?

A

quaternary structure proteins made up of four polypeptide chains

42
Q

what does every antibody have that is different?

A

each different antibody has a different shaped binding site, which
is the variable region

the shape of the antigen-binding site is unique to the shape of a particular antigen

43
Q

what is the process called that makes lots of antibodies clump together?

A

agglutination

44
Q

why is agglutination important?

A

this makes it easier for phagocytes to locate and destroy the pathogens

45
Q

what is passive immunity?

A

antibodies are introduced into the body

the pathogen doesn’t enter the body, so plasma cells and memory cells are not made

e.g. antibodies passed to a fetus through the placenta
or through breast milk to a baby

46
Q

is passive immunity long term immunity?

A

no

47
Q

what is active immunity?

A

active immunity is when immunity is created by your own immune system following exposure to the pathogen or its antigen

48
Q

what are the two types of active immunity?

A

natural and artificial

49
Q

what is natural active immunity?

A

following infection and the creation of the body’s own antibodies and memory cells

50
Q

what is artificial active immunity?

A

following the introduction of a weakened version of the pathogen or antigens via a vaccine

51
Q

what are vaccines?

A

small amounts of weakened or dead pathogens or antigens are introduced in the mouth or by injection

52
Q

how does having a vaccine cause your body to produce antibodies and become immune to that specific pathogen?

A
  • exposure to the antigens activates the B cell to go through clonal expansion and differentiation (clonal selection)
  • B cells undergo mitosis to make large numbers of cells, these differentiate into plasma cells or memory B cells
  • plasma cells make antibodies
  • B memory cells divide rapidly into plasma cells when re-infected with the same pathogen to make large numbers of antibodies rapidly
53
Q

what is herd immunity?

A

if enough of the population is vaccinated the pathogen cannot spread easily amongst the population

54
Q

who does herd immunity protect?

A

provides protection for those who are not vaccinated e.g those already too ill to have a vaccine or who have a lowered immunity, or those who are too young

55
Q

what is a monoclonal antibody?

A

a monoclonal antibody is a single type of antibody that can be
isolated and cloned

56
Q

what are antibodies made from?

A

proteins which have binding sites complementary in shape to certain antigens

57
Q

what are some uses of monoclonal antibodies?

A

medical treatment

medical diagnosis

pregnancy tests

58
Q

how can direct monoclonal antibody therapy be used to help deliver medication to cancer patients?

A

some cancers can be treated using monoclonal antibodies which are designed with a binding site complementary in shape to the antigens on the outside of cancer cells

the antibodies are given to the cancer patient and attach to the cancer cells, while the antibodies are bound to the cancer antigens,
this prevents chemicals from binding to the cancer cells which enables uncontrolled cell division

therefore, the monoclonal antibodies prevent the cancer cells from growing, and as they are designed to only attach to cancer cells they do not cause harm to other normal cells

59
Q

how can indirect monoclonal antibody therapy be used to help deliver medication to cancer patients?

A

cancer can also be treated with monoclonal antibodies complementary in shape to the antigens on the outside of cancer cells which have drugs attached to them

these cancer drugs are therefore delivered directly to the cancer cells and kill them

this reduces the harmful side effects that traditional chemotherapy and radiotherapy can produce, this is often referred to as ‘bullet drugs’

60
Q

what can monoclonal antibodies be used to test for?

A

pregnancy

influenza

hepatitis

chlamydia

prostate cancer

61
Q

how does an ELISA test use three different types of antibodies in a pregnancy test?

A

first mobile antibody, complementary to the antigen being tested for, and has a coloured dye attached

a second antibody complementary in shape to the antigen is immobilised in the test

a third antibody is immobilised and is complementary in shape to the first antibody

62
Q

what are the ethical issues to do with monoclonal antibodies?

A

creating monoclonal antibodies requires mice to produce the antibodies and tumour cells, which leads to ethical debates

63
Q

where do viruses replicate?

A

inside cells

64
Q

why can viruses not be destroyed by antibiotics?

A

they have no cell wall

65
Q

what is the core in HIVs structure?

A

genetic material (RNA) and the enzyme reverse transcriptase, which are needed for viral replication

66
Q

what is the capsid in HIVs structure?

A

the outer protein coat

67
Q

what is the envelope in HIVs structure?

A

extra outer layer, made out of lipids taken from the host’s cell membrane

68
Q

what are the protein attachments in the HIV structure?

A

on the exterior of the envelope to enable the virus to attach to the host’s helper T cell

69
Q

how is HIV transported through the body?

A

through the blood until it attaches to a CD4 protein on the helper T cells

70
Q

during HIV replication what fuses with the helper T cell membrane?

A

the HIV protein capsule then fuses with the helper T
cell membrane, enabling the RNA and enzymes from HIV
to enter

71
Q

what does the HIV enzyme reverse transcriptase do?

A

copies the viral RNA into a DNA copy and moves to the helper T cell
nucleus, this is why it is called a retrovirus

72
Q

what do helper T create during HIV replication?

A

creates viral proteins to make new viral particles

73
Q

how does AIDS occur from HIV?

A

AIDS is when the replicating viruses in the helper T cells interfere with the normal functioning of the immune system

74
Q

what causes people to die from AIDS?

A

the destruction of the immune system that leads to death, rather than HIV directly

75
Q

why are people with HIV more vulnerable to other diseases?

A

with the helper T cells being destroyed by the virus, the host is unable to produce an adequate immune response to other pathogens and is left vulnerable to infections and cancer

76
Q

what are symptoms of AIDS?

A

skin - tumors

gastrointestinal - chronic diarrhea

central - meningitis

77
Q

What is the function of reverse transcriptase?

A

It synthesizes DNA from an RNA template

This enzyme is crucial for retroviruses like HIV.

78
Q

What are the components of a virus mentioned?

A
  • Transmembrane glycoprotein
  • Capsid
  • Genetic material

These components are essential for the structure and function of viruses.

79
Q

What does HIV target in the human body?

A

Helper T cells

HIV specifically infects and destroys these immune cells.

80
Q

What is the normal range of helper T cells per mm³ in healthy humans?

A

800 - 1200 helper T cells

This range indicates a functioning immune system.

81
Q

What T cell count indicates progression to AIDS?

A

Less than 200 helper T cells

This low count signifies a severely weakened immune system.

82
Q

What is the consequence of HIV on B cells?

A

B cells cannot be stimulated to produce antibodies

This leads to impaired immune response.

83
Q

What happens to cytotoxic T cells and memory cells during HIV infection?

A

They are sometimes infected and destroyed

This results in inadequate immune response.

84
Q

What results from the destruction of helper T cells by HIV?

A

Inadequate immune response

This leaves the body vulnerable to infections and cancers.

85
Q

In AIDS patients, what types of infections are they prone to?

A
  • Infections of the lungs
  • Infections of the intestines
  • Infections of the brain
  • Infections of the eyes

These infections are common due to the weakened immune system.

86
Q

True or False: It is HIV that directly causes death in AIDS patients.

A

False

It is secondary infections and illnesses, not HIV, that lead to death.

87
Q

What is the role of the protein capsid in HIV infection?

A

Fuses with the cell membrane

This process allows the HIV virus to enter the host cell.

88
Q

What happens after HIV RNA and enzymes enter the T cell?

A

The mRNA leaves the nucleus of the host cell through nuclear pores

It utilizes the cell’s protein synthesis mechanisms to create HIV particles.

89
Q

Where is the new DNA from HIV moved after it is created?

A

Into the helper T cell’s nucleus

This insertion is into the cell’s DNA.

90
Q

What does the HIV DNA in the nucleus create?

A

mRNA using the cell’s enzymes

This mRNA contains instructions for making new viral proteins.

91
Q

What are attachment proteins on HIV that bind to T helper lymphocytes?

A

gp120 molecules

These proteins specifically bind to CD4 receptor proteins.

92
Q

What process occurs when HIV particles bud away from the helper T cell?

A

They form their lipid envelope

This occurs by taking a piece of the cell’s cytoplasmic membrane.

93
Q

What enzyme does HIV use to convert its RNA to DNA?

A

HIV reverse transcriptase

This is a critical step in the HIV replication process.

Biology (8 decks)

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