Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Biology - Year 12 > Cell recognition and the immune system - Chapter 5 > Flashcards

Cell recognition and the immune system - Chapter 5 Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Biology flashcards Biology 101 flashcards
1
Q

What is immunity?

A

The body’s ability to identify and protect itself against disease

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the immune system ?

A

The system in the body responsible for maintaining homeostasis by recognising harmful from non-harmful organsims and produces an appropriate response

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What are pathogens ?

A

Viruses, bacteria or other living things that cause disease/ immune system

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Defence mechanisms

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are the two types of defence mechanisms?

A

Specific + non -specific

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is a non-specific defence mechanism?

A

Does not distinguish between one type of pathogen and another responds to all pathogens in the same way + quickly

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is a specific defence mechanism ?

A

It does distinguish between different pathogens long lasting immunity and slow response

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What are the 2 forms of non-specific defence mechanisms ?

A
  1. Barriers to entry to the bloodstream
  2. Phagocytosis
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What are the barriers to entry task (body) ?

A
  • skin : many dead cells, protective layer for the majority of the body surfaces
  • saliva : antibacterial enzymes
  • tears : antibacterial enzyme: lysozyme. tear ducts : flushes out things in enzymes
  • mucus : linings traps dirt + microbes , nasal hair …
  • stomach acid : low pH kills harmful microbes. Contains hydrochloric acid, helps to kill any pathogens in food/water
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

When you get a cut, how does the body respond ?

A

By clotting the blood to prevent/ reduce the entry of pathogens

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What does blood clotting involve (and the definition )?

A

Involves platelets found in the bloodstream.
Platelets: tiny, short-lived fragments of cells, with no nucleus, formed in the bone marrow + released in the blood

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What does tissue damage result in ?

A

Inflammation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

When tissue is damaged, what type of cells are activated , and what do they release ?

A

Mast cells are activated, releasing the chemicals histamine + cytokines

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What does histamine do?

A

~> Causes capillaries to dilute
~> this increases blood supply (to infected area)
~> causes area to feel hot + red
The increased temperature reduces the ability of pathogens to reproduce.

Histamine also makes blood vessel walls more permeable.
~> allows more blood plasma to leave blood + form tissue fluid, causes tissues to swell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What do cytokines do ?

A

Attract phagocytes to the damaged tissue .
~> Phagocytes invade tissue
~> Phagocytosis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is the flow chart of response?

A

Tissue damage ~> inflammation ~> phagocyte ~> phagocytosis ~> pathogen destroyed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What are the steps of inflammation?

A

Damaged cells ~> histone ~> capillaries dilate ~> increased blood supply
~> chemokines ~> Attract phagocytes ~> Phagocytes invade tissue
~> Phagocytosis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What are inflammation side effects

A

Red, when touch it (your skin), it is hot

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Why does your skin turn red when inflamed?

A

Due to increased blood flow because of phagocytes.
Chemokines attract the phagocyte

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is phagocytosis ?

A

Is a form of endocytosis in which a phagocyte ( type of white blood cell) engulfs + digests a pathogen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Where are phagocyte produced ?

A

In the bone marrow
They are distributed around the body in the blood

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What are phagocytes responsible for?

A

Responsible for removing dead cells + invasive microorganisms.
They carry out a non-specific immune system

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What are the phagocytosis stages ?

A
  1. Phagocyte (neutrophils) detects chemicals released by pathogen and moves towards it (chemotaxis)
  2. [There are many receptor binding points on the surface of the phagocytes]
    The phagocyte attaches to the antigen on the pathogen via these receptors
  3. Phagocyte engulfs pathogen to form a vesicle ( a phagosome)
  4. Lysosomes move to phagosome and fuses with it (forms phagolysosome and release their contents into it. )
  5. The lysozyme in the lysosome destroysthe pathogen (by hydrolysis of their cell walls)
  6. The breakdown products are absorbed and used by the phagocyte
  • After killing and digesting the pathogens, the phagocytes (neutrophils) die
  • Pus is an accumulation of a sign of dead neutrophils
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

what is a non - specific response ?

A

Phagocytosis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What are two specific responses, and what WBC is used ?

A

WBC used : lymphocyte

  1. Cell - mediated responses , involving T lymphocytes
  2. Humoural responses, involving B lymphocytes
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

What are lymphocytes , and where are they produced ?

A

Is a type of white cell, produced by stem cells in the bone marrow

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Why are T lymphocytes called this? (Where do they mature ?)

A

They mature in the thymus gland. They are associated with cell -mediated immunity, that is immunity involving body cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

Why are B lymphocytes so called this ? (Where do they mature ?)

A

They mature in the bone marrow. They are associated with humoural immunity (immunity involving antibodies that are present in body fluids)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

What is an antigen ?

A

Foreign protein on the surface of an organism that stimulates on immune system

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

When do antigens become a problem, and how can we solve this?

A

F a problem during blood transports + organ systems

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

What is a self-antigen ?

A

A molecule found on the surface of your cells to which you do not respond.
It has a specific shape ; self recognition.
BUT it will cause a response if introduced into another human

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

What is a non- self antigen ?

A

A molecule found on cells entering your body that are not yours. E,g, bacteria, viruses or another oerson’s cells. This will produce an immune destined (you don’t need to respond )

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

What are antibodies ?

A

Protein made by B lymphocytes in response to the presence of a specific antigen (when non-self material has invaded the body)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

Describe and explain the role of antibodies in stimulating phagocytosis

A

Bind to antigen, antibodies cause agglutination/ attract phagocytes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

What do antibodies consist of (chains) , and what are they ?

A

Consists of 4 polypeptide chains :
A pair of heavy chains (long)
A pair of light chains (short)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

What are the chains held together by ?

A

Disulphide bridges

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

What is the role of the disulphide bridge in forming the quaternary structure of an antibody ?

A

Joins two (different) polypeptides

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

What does the 2 antigen binding sites mean to the antibody ?

A

That one antibody molecule binds to 2 identical antigen molecules

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

Explain the antigen- antibody complex

A

When antigens bind, we call this an antigen-antibody complex.
The tertiary structure of the antigen-binding site is complementary to the structure of the antigen.

Simple terms:
The antigen fits perfectly into the antigen-binding site, meaning that antibodies are highly specific for the antigen they bind to

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

What is the hinge region, and what does it allow?

A

Where the heaving chain and light chain bend (in the middle of it).
It is flexible, allowing the distance between the two antigen binding sites to vary

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

What happens when antibodies are flexible + can bind to multiple antigens to clump together ?

A

This makes it easier for phagocytes to locate + destroy the pathogens

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

What is the constant region (in an antibody) ?

A

Where both antibodies have a region which is the same
Constant region has the same structure for every antibody, no matter which B lymphocyte produced it

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

What are variable regions ?

A

Where the ends of the antibody molecules are differeng

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

What do variable regions form , and what does this mean ?

A

The antigen - binding sites [ the shape of the variable regions are different for the antibodies produced by different B lymphocytes],
meaning antibodies produced by B lymphocytes will bind to different antigens

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

What are the 4 main functions in an antibody ?

A
  • act as opsonins, tagging foreign bodies for phagocytosis
    (helps phagocytes - make tracking + ingesting pathogens easier)
  • causes agglutination : antibodies can stick pathogens together (in clumps) preventing them from spreading around the body (makes it easier for the phagocyte to locate them as they are less spread-out within the body )
  • by sticking pathogens such as viruses, antibodies prevent them from invading host cells
  • Antibodies can stick to bacterial toxins, preventing the toxins from harming body cells
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
46
Q

What are monoclonal antibodies ?

A

Antibodies with the same tertiary structure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
47
Q

What is the experiment that produces monoclonal antibodies ? (Mouse experiment)

A
  • inject a mouse with an antigen, then lymphocytes will produce antibodies against the antigen
  • then collect the lymphocytes from the mouse
  • so in the next stage, we fuse our lymphocytes with a tumour (cancer) cell
  • cell produced : hybridoma -> they produce antibodies + divide by mitosis
  • next stage : select a single hybridoma cell producing the antibody that we want
  • Allows this hybridoma cell to divide by mitosis, forming a clone of identical hybridoma cells
  • antibodies produced are all identical
  • then they collected + purified
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
48
Q

What is a problem with lymphocytes in the monoclonal antibodies experiment ?

A

They do not divide by mitosis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
49
Q

Why is the benefit of using cancer cells in the monoclonal antibodies experiment ?

A

Cancer cells are very good at dividing by mitosis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
50
Q

What are monoclonal antibodies uses ?

A

1) For cancer treatment : targets cancer cells
2) immunoassay: e.g drug + pregnancy tests [calculating the amount of substance in a mixture]
3) medical diagnosis

51
Q

What are ethical issues of monoclonal antibodies ?

A
  • production : use of mice
  • genetic engineering : human genes inserted into mice to produce human antibodies
  • some deaths associated with multiple sclerosis treatment
  • safety issues of testing new drugs …. informed decisions
52
Q

Cell mediated response immunity

A
53
Q

What are lymphocytes ?

A

They are white blood cells involved in the specific immune system

54
Q

What type of lymphocytes are involved in cell - mediated response ?

A

T lymphocytes (T cells)

55
Q

Where are lymphocytes made?

A

Bone marrow

56
Q

Where do T cells mature ?

A

In the thymus

57
Q

What is the cell mediated response (definition) ?

A

Is the response involving T cells + body cells

58
Q

Why are cell-mediated response specific ?

A

Because T cells respond to antigens on the surface of cells

59
Q

What is an antigen presenting cell (APC) ?

A

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

60
Q

What are some examples of APC?

A
  • infected body cells will present the viral antigens on their surface
  • a macrophage which has engulfed + destroyed a pathogen will present the antigens on their surface
  • cells of a transplanted organ will have different shaped antigens on their surface compared to your self-cell antigens
  • cancer cells will have abnormal shaped self-cell antigens
61
Q

What does APC trigger ?

A

The cell mediated response

62
Q

What does cell meditated mean ?

A

The antigen attached to the cell

63
Q

Why are T cell responses described as ‘cell-mediated’ ?

A

Because T cells only respond to antigens which are presented on APC, and not antigens attached from cells within body fluids . E.g the blood

64
Q

What are the steps in the cell mediated response ?

A
  1. Once the pathogen has been engulfed + destroyed by a phagocyte, the antigens are positioned on the cell surface, APC (on plasma membrane ? )
  2. Helper T cells have receptors on their surface which can attach to the antigens on APC
  3. Once attached, this activated the helper T cells to divide by mitosis to replicate + make large number of cloned
  4. Cloned helper T cells can differentiate into different cells
65
Q

What different types of cells can cloned T helper cells differentiate into ?

A
  • some remain as helper T cells + stimulate B cells to divide (cytokines),
  • Some stimulate macrophages to perform more phagocytosis (vis cytokines)
  • some become memory cells far that shaped antigen
  • some become cytotoxic T cells (killer T cells), they kill infected cells
66
Q

How do Killer T cells destroy and how do they work ?

A

They destroy abnormal or infected cells

They work by producing a protein, perforin, which embeds in the cell surface membrane and makes a pore (holes) so that any substances can enter or leave the cell

67
Q

What is a consequence of killer T cells?

A

The cell becomes freely permeable to all substance + eventually died

68
Q

What do killer T cells cause ?

A

Cell death

69
Q

What are killer T cells most common in?

A

Most common in viral infections because viruses infect body cells , viruses replicate within body cells, causing dying infected cells

70
Q

Humoral response to immunity

A
71
Q

Where are B lymphocytes made , and where do they mature ?

A

In the bone marrow

72
Q

What is the humoral response?

A

The Humoral response is the response involving B cells + antibodies.
Antibodies are soluble + transport in bodily fluids in blood.
‘Humour’ is and old term for bodily fluids, so Humoral response

73
Q

What is the Humoral response steps (B-cell activation) ?

A

[10 million different B cells, which have antibodies on their surface are complementary to 10 million different antigens ]

  1. At some point, a pathogen will encounter the B cell with the correct antibodies binding to the antigen on the pathogens surface.
    Now the B cell attaches to the pathogen and the pathogen is engulfed.
  2. The pathogen is digested and the antigens are presented on the surface of the B cell.
    B cell now acts as an APC.
  3. Antigens in the blood collide with their complementary antibody on a B cell. The B cell takes in the antigen by endocytosis + presents it on its cell -surface membrane
  4. When this B cell collides with a helper T cell receptor, this activates the B cell to go through clonal expansion + differentiation (clonal selection )
  5. B cells undergo mitosis to make large numbers of cells, they differentiate into plasma cells or memory B cells
74
Q

What do plasma cells make ?

A

Antibodies

75
Q

How are B memory cells associated with plasma cells and antibodies (how do they make them) ?

A

B memory cells can divide rapidly into plasma cells when re-infected with the same pathogen to make large numbers of antibodies rapidly

76
Q

How long can memory B cells live for vs plasma cells ?

A

Memory B cells can live for decades in your body, whereas plasma cells are short lived

77
Q

What do memory B cells not make, but what do they make instead?

A

They do not make antibodies, they divide by mitosis + make plasma cells rapidly if they collide with an antigen they have previously encountered

78
Q

What does memory B cells result in ?

A

Active immunity : memory B cells make plasma cells, which results in large numbers of antibodies produced so rapidly that the pathogen is destroyed before any symptoms can occur

79
Q

What happens in primary immune response ( in the primary + secondary immune response graph ) ?

A

Plasma cells make antibodies, life span is short

80
Q

What happens in secondary immune response ( in the primary + secondary immune response graph ) ?

A

Memory cells produce plasma cells, producing antibodies -> faster rate

81
Q

What is the pathway of specific immune response ?

A

1) pathogens eaten by phagocyte
2) displays antigen of pathogen on surface
3) helper T cell recognises antigen, stimulating further phagocytosis
4) this activates B cell ( producing memory and plasma cells, plasma cells producing antibodies)
This also activates cytotoxic T cells (killer T cells)

82
Q

What does infection with a pathogen trigger ?

A
  • B lymphocytes to produce antibodies, they specifically target antigens on the pathogen
  • T lymphocytes to become activated :
    T cells produce cytokines (which stimulate B cells)
    T cells also stimulate killer T cells, and T cells form memory cells
83
Q

Vaccination

A
84
Q

What is active immunity ?

A

Immune system has created the antibodies due to exposure to the pathogen
(B + T cells were activated, and antibodies were produced + memory cells were formed )

85
Q

What are the two types of active immunity ?

A
  1. Natural active immunity
  2. Artificial active immunity
86
Q

What is natural active immunity ?

A

Being infected with a pathogen [ + creation of the bodies own antibodies + memory cells ]

87
Q

What is artificial active immunity ?

A

Vaccination [ is a medical procedure, not a natural process ]
Following the introduction of a weakened version of the pathogen or antibodies via a vaccine ~> herd immunity

88
Q

What is passive immunity ?

A

The immune system is not activated. The pathogen doesn’t enter the body [plasma cells and memory cells are not made ]
Antibodies are introduced into the body

89
Q

What is natural passive immunity ? (2 examples)

A

In babies:
1. New born babies cannot make antibodies effectively as their immune system is not fully developed. Instead, the baby in the foetus receives antibodies from the mother through the placenta.
Provides protection for the first few months of life.

  1. In first few days baby is born, the mother’s breast milk is very rich in antibodies : milk + colostrum. The antibodies in colostrum pass from the baby’s digestive system into the baby’s bloodstream. So, because the baby has received antibodies from its mother, the baby has some immunity to pathogens.
90
Q

What is artificial passive immunity ?

A

If antibodies are needed immediately, then they can give ready-made antibodies

91
Q

What is a vaccines?

A

They are small amounts of weakened/ dead pathogens or antigens, which are introduced in the mouth or by injection.

92
Q

What do vaccines stimulate ?

A

The immune system, activating T + B cells

93
Q

What are vaccines used to prevent ?

A

Epidemics + pandemics

94
Q

What is an epidemic ? (And an example )

A

When an infectious disease spreads rapidly in a population either in a specific location e,g, city or across a whole country.

E.g. New Zealand : measles

95
Q

What is a pandemic ? (And an example)

A

When an infectious disease spreads rapidly across several countries, a continent or whole world.

E.g. COVID pandemic

96
Q

How do vaccines work?

A

Usually given via the mouth or as an injection into the bloodstream

97
Q

What do vaccines contain ?

A

They contain antigens from the pathogens that we want to protect the body against

98
Q

Other than antigens, what other things to vaccines contain (4 points) ?

A
  1. Some vaccines contain a weakened strain of a virus/bacteria, so can affect the patient (but is easily fought off by the immune system )
  2. Other vaccines contain bacterial cells (which have been killed). [In this case, the pathogen cannot cause an infection, but the antigens can trigger an immune response ]
  3. Other vaccines only contain antigen molecules. These antigens may be extracted from the pathogen or manufactured using genetic engineering
  4. Some vaccines provide protection against a bacterial toxin.
    [In this case, the vaccine contains toxin molecules which have been modified, making the toxin harmless, but still allow them to act as an antigen.]
99
Q

Once the vaccine enters the body, what does this stimulate ?

A

A primary response

~> leads to production of antibodies + memory B cells
~> T cells also activated

100
Q

If the person later comes into contact with the pathogen, then what is triggered ?

A

The secondary immune response

101
Q

What makes a vaccination programme successful ?

A
  • Availability of vaccine : cost + quantity
  • lack of side- effects
  • production, storage + transport of vaccine
  • Administration of vaccine- staff availability
  • Herd immunity must be possible
102
Q

What is herd immunity ?

A

If enough of the population are vaccinated, the pathogen cannot spread easily amongst the population (providing protection for those who are not vaccinated. E.g. those who are too ill to have a vaccine, or have lowered immunity unable, or those who are too young. )

103
Q

When does herd immunity only work ?

A

If a high enough percentage of people have been vaccinated

104
Q

Why does a pathogen’s DNA change the shape of an antigen ?

A

It can mutate frequently

105
Q

What is antigenic variability?

A

The mechanism that pathogens use to alter their surface proteins to evade the host immune response.
E.g. the influenza virus mutates regularly + changes its surface antigens

106
Q

Due to antigenic variability, what do people need to be ?

A

Revaccinated every year with an updated influenza virus

107
Q

Why is there no effective vaccine for common cold ?

A

The common cold is caused by a virus (but over a hundred types of the cold virus). Each of these types of the common cold virus has different surface antigens, so this is why there is no effective vaccine for common cold.

108
Q

Why is disease not eradicated (gotten rid of ) ?

A
  • Detective immune system of individuals
  • Different varieties of pathogens. E.g. cold virus
  • Pathogen mutates frequently
  • Some pathogens conceal themselves in other cells
  • Some people avoid vaccines - religious grounds
109
Q

What is HIV, and what does it cause ?

A

Human immunodeficiency Virus

It is an RNA virus , a virus that causes AIDS

110
Q

What are the types of organelles in HIV?

A

-RNA
-Capsid (protein capsid)
- reverse transcriptase (enzyme)
- Matrix proteins - helps to maintain the structure of the virus
- lipid envelope
- attachment proteins - allow HIV to attach to its host cell

111
Q

What is the replication of HIV?

A

[Once a person is infected, HIV particles circulate in the bloodstream]
-The attachment protein on HIV attaches to a molecule : CD4, via receptors on helper T cell
- [ Once HIV attaches to CD4, the HIV lipid envelope fuses with the cell membrane ]
- [The protein capsid passes into the cell, then fuses with the helper T cell membrane ] , enabling RNA + enzymes from HIV to enter
- The reverse transcriptase enzyme converts the viral RNA into DNA , why its called retrovirus
- [The DNA now moves into the cell nucleus and integrates with the host DNA ]
- Here the mRNA is transcribed, and the helper T cell starts to create viral proteins to make new viral particles
- The virus particles assemble and then bud from the helper T cell, and are released from the cell, causing a lipid envelope to form

112
Q

Once HIV becomes active +replicates, what does this lead to ?

A

The death of helper T cells

113
Q

What does the death of helper T cells result in ?

A

As the number of helper T cells decreases, the patient’s immune system can no longer function effectively.
Without enough helper T cells, antibody production by B cells + cell -mediated immune response becomes less effective, causing the patient to have AIDS

114
Q

How does HIV cause AIDS, and what are they more vulnerable to ?

A

Kills or interferes with the normal function of helper T cells.
Patient with AIDS are more vulnerable to tuberculosis + higher risk of developing cancer

115
Q

Why can antibiotics not be used to treat viral infections ?

A

They kill bacteria : target bacterial cell structures

E.g. penicillin prevents cross-linking of peptidoglycon molecules in bacterial cell wall. Causing bacterial cell to burst when water enters by osmosis

116
Q

Why can viruses not be treated using antibiotics?

A

They don’t have any cellular structure, so take advantage of the metabolic process of their host cell

117
Q

How do we treat viral diseases?

A

Using antiviral drugs.

-antiviral drugs against HIV inhibit key enzymes in the HIV replication cycle
e.g. reverse transcriptase

118
Q

What is a consequence of having insufficient helper T cells?

A

Cannot stimulate B cells to make antibodies, killer T cells to kill cells + memory cells can be destroyed
Therefore, the body cannot produce an adequate immune response and is open to secondary disease

119
Q

What is an ELISA test ?

A

Used to see if a patient has only antibodies to a certain antigen

120
Q

What happens in an ELISA test?

A

A coloured product is formed when enzyme reacts with certain substrate, causing solution in reaction vessel to change colour.

If colour change occurs, shows that the antigen or antibody of interest is present in the sample being tested.

121
Q

What are ELISA tests carried out using and why?

A

Plastic plates - has a number of small wells : allows us to analyse a number of samples in one go

122
Q

What are the steps in an ELISA test?

A

1) First HIV antigens are bound to the bottom of the reaction vessel [material on bottom of vessel is designed so that antigen molecules stick]
2) Wash well several times, removing any antigen molecules that did not stick
3) A blood plasma sample is taken from the patient + added to the reaction vessel
4) Any HIV- specific antibodies present in the blood plasma now bind to the HIV antigens : primary antibodies
5) Any other antibodies present in the blood plasma are unbound and washed out
6) Now add a 2nd antibody (secondary antibodies) has on enzyme attached to it, add to the blood vessel
7) These secondary antibodies specifically bind to the first antibody. The reaction vessel is washed out again to remove any unbound secondary antibodies (if not washed out, would give a positive result) .
8) Finally, a solution is added that contains a substrate for the enzyme. Substrate is normally a colourless molecule the enzyme converts the substrate into a product molecule which is coloured, causing the solution in the reaction vessel to change colour.
~> Indicates patient has HIV - specific antibodies in the blood

123
Q

What does the intensity of the colour produced in the ELISA test depend on ?

A

Depends on the number of enzyme molecules, which in turn depends on the number of antigen molecules present

124
Q

What makes the ELISA test a quantitative test ?

A

The intensity of the colour can be used to determine the amount of antigen, making the ELISA test a quantitative test

Biology - Year 12 (12 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions