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Key Knowledge 7 Flashcards

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1
Q

pathogen 

A

an agent that causes disease

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2
Q

antigen 

A

any molecule that may trigger an immune response

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3
Q

non-self antigen 

A

a molecule from outside the body that is recognised by the immune system and initiates an immune response. Also known as a foreign antigen

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4
Q

major histocompatibility complex (MHC) proteins 

A

a group of proteins present on the surface of all self-cells that enables the immune system to distinguish it from non-self material. Also known as self-antigens

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5
Q

autoimmune disease 

A

a disease in which an individual’s immune system initiates an immune response against their own cells

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6
Q

allergen 

A

a non-pathogenic antigen that triggers an allergic reaction

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7
Q

allergic reaction

A

an overreaction of the immune system to a nonpathogenic antigen

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8
Q

cellular pathogen 

A

a pathogen that has a cellular structure and exhibits the processes of a living organism. Examples include bacteria, fungi, protozoa, and parasites

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9
Q

non-cellular pathogen

A

a pathogen that neither has a cellular structure nor exhibits the processes of a living organism. Examples include viruses and prions

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10
Q

Bacteria

A

Unicellular prokaryotes that can infect almost any part of the body. Bacteria can cause disease through the production of toxins and enzymes which either affect the functioning of cells or
cause their death

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11
Q

Fungi

A

Eukaryotic organisms that include yeasts and moulds and contain long, branching filaments called hyphae.

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12
Q

Worms

A

Multicellular invertebrate parasites whose development include egg, larval, and adult stages. Can vary in length, with the longest worms being over 55 m in length

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13
Q

Protozoa

A

Single-celled eukaryotes that can be free-living or parasitic. Protozoa have many different mechanisms of action – for example, some can inhibit nucleic acid synthesis, protein synthesis, and various stages of cellular respiration.

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14
Q

Viruses

A

An infectious agent composed of genetic material (DNA or RNA) inside a protein coat (capsid). In some instances the protein coat is surrounded by a lipid envelope. Viruses are not able to independently reproduce, instead they insert their genetic material into a host’s cell and use the cell to replicate

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15
Q

Prions

A

Abnormally folded proteins that have the ability to induce normal proteins nearby to become misfolded. They only occur in mammals and affect only the brain and other neural structures. They are currently the only known infectious agents that don’t contain nucleic acids

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16
Q

innate immune system

A

a component of the immune system that is composed of generalised and non-specific defences and/or responses to pathogens. Also known as the non-specific immune system.

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17
Q

first line of defence 

A

a component of the innate immune system characterised by the presence of physical, chemical, and microbiological barriers to keep pathogens out of the host organism

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18
Q

second line of defence 

A

a component of the innate immune system characterised by the nonspecific response to injury and/or pathogens by a variety of cells and molecules

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19
Q

physical barrier 

A

a component of the first line of defence that features solid or fluid obstacles that block pathogen entry such as skin or mucus

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20
Q

chemical barrier 

A

a component of the first line of defence that features the use of enzymes, toxins, and acids to protect against pathogen invasion

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21
Q

physical example (plants)

A

• Thick bark
• Waxy cuticles of leaves
• Formation of galls to prevent the spread of infection
• Presence of thorns and trichomes to deter insects and grazers
• Closing of stomata to prevent pathogen invasion during carbon dioxide uptake

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22
Q

chemical example (plants)

A

• Chitinases – enzymes that occur in a number of different plants and have antifungal properties
• Phenols – secreted by wounded plants, repelling or killing invading
microorganisms
• Defensins – small peptides that are toxic to microbes and fungi
• Saponins – disrupt the cell membranes of various fungi
• Oxalic acid – a substance that can be toxic if ingested
• Glucanases – defend plants against fungi

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23
Q

microbiological barrier 

A

a component of the first line of defence in which the presence of normal flora limits the growth of pathogenic bacteria

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24
Q

physical examples (humans)

A

• Intact skin and surfaces between external and internal environments (e.g. integumentary, respiratory, gastrointestinal, and genitourinary tracts)
• Mucous secretions and/or hairs in the respiratory tract that trap organisms, and cilia that sweep them away from the airways and into the throat where they are
swallowed and destroyed by the gastrointestinal tract

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25
chemical example (humans)
• Presence of lysozyme enzymes in tears and saliva that destroy bacterial cell walls • Acidic sweat that destroys pathogens growing on the surface of the body • Stomach acid that destroys pathogen that have been eaten/swallowed • Antibacterial compounds in earwax • Antibacterial proteins in semen • Low pH in the vagina
26
microbiological example (humans)
• Presence of bacteria on the skin, in the lower gastrointestinal tract, and the vagina
27
leukocytes 
a group of blood cells responsible for protecting the body against pathogens and foreign material. Also known as white blood cells
28
phagocyte 
a group of leukocytes responsible for the endocytosis and destruction of pathogens, foreign material, and cell debris
29
neutrophil 
the most common type of leukocyte in the body. Engages in phagocytosis of pathogens and foreign material, as well as the release of cytokines
30
macrophage 
a type of leukocyte found throughout the body that engages in phagocytosis and antigen presentation
31
dendritic cell 
a type of leukocyte that engages in phagocytosis and antigen presentation
32
antigen-presenting cell 
a subgroup of phagocytes that display antigens from consumed pathogens on their surface and interact with the adaptive immune system
33
cytokine 
a signalling molecule released by cells (typically in the immune system) which aids in communication between immune cells and helps protect against pathogens
34
natural killer (NK)
a type of leukocyte responsible for the recognition and destruction of damaged and/or infected host cells 1. Interaction between NK cell and infected cell 2. Binding of killer activation receptor to stress molecules 3. Insufficient binding of killer inhibitory receptor to MHC I markers, leading to cell death
35
mast cell 
a type of leukocyte responsible for releasing histamine during allergic and inflammatory responses
36
degranulation 
the release of granule contents from a cell
37
histamine 
a molecule released by mast cells that plays a key role in inflammation
38
inflammatory response 
a series of biochemical events that occur in the body as a result of infection and/or trauma. Characterised by swelling, redness, pain, and heat in the affected tissue
39
eosinophil 
a large granular leukocyte responsible for the release of toxic chemical mediators
40
interferon 
a cytokine released by virally infected cells that increases the viral resistance of neighbouring uninfected cells
41
complement proteins 
a number of different types of proteins found in the blood that opsonise, cause lysis, and attract phagocytes to invading pathogens
42
complement cascade 
a complex sequence of events which occurs after the activation of complement proteins
43
opsonisation 
Complement proteins stick on the outside surface of pathogens and make it easier for cells of the immune system, such as phagocytes, to recognise them as foreign
44
Chemotaxis
Complement proteins gather near a pathogen and attract phagocytes to it, making it more likely to be destroyed.
45
Lysis
Complement proteins can join together on the surface of pathogens, forming a membrane attack complex (MAC), which creates pores in their membrane. This destroys the pathogen by causing lysis via the sudden influx of fluid into the pathogen, causing it to burst.
46
membrane attack complex (MAC) 
a pore formed by complement proteins in the cell membranes of a pathogen, disrupting the membrane and leading to the pathogen’s destruction
47
Initiation
The splinter pierces the skin, damaging cells and introducing pathogens such as bacteria into the body. In response to this injury, both immune cells located in the tissue and damaged cells release cytokines. Additionally, mast cells degranulate, releasing histamine.
48
Vasodilation
The histamine released from mast cells travels to nearby blood vessels and binds to specific receptors, causing vasodilation. This causes blood vessels to widen, increasing blood flow to the injury site, and this is the reason behind the swelling, redness, and warmth we often associate with inflammation. Additionally, the formation of gaps in the vessel wall increases its permeability to cells of the immune system.
49
Migration
Vasodilation and the increased leakiness of blood vessels allow for a number of innate immune system components to leave the bloodstream and enter the site of injury. These components include: • Phagocytes are guided by the cytokines secreted by damaged cells to the site of injury, where they phagocytose pathogens. • Complement proteins are attracted to pathogens and make it easier for phagocytes to destroy them
50
third line of defence 
a subset of the immune system within vertebrates that is composed of the humoral and cell-mediated responses which create a specific immune response and form immunological memory.
51
immunological memory 
the ability of the immune system to quickly and aggressively combat a previously encountered pathogen due to the presence of T and B memory cells
52
T lymphocyte 
a type of lymphocyte that plays an important role in cell-mediated immunity. It differentiates into cytotoxic T cells, T memory cells, and T helper cells
53
T helper cell (Th) 
a type of differentiated T lymphocyte that supports the functioning of a number of different immune cells, including the cloning and differentiation of selected T and B cells
54
antigen-presenting cell 
a subgroup of phagocytes that display the antigens from consumed pathogens on their surface and interact with the adaptive immune system
55
lymphatic system 
a large network of vessels and tissues throughout the body that form an important component of both the circulatory and immune systems
56
lymph node 
a small secondary lymphoid tissue of the lymphatic system where antigen-presenting cells activate the adaptive immune system
57
humoral immunity 
an adaptive immune response in which extracellular pathogens are targeted by specific antibodies produced by plasma cells. 1. Selection of a B cell 2. Stimulation of the selected B cell through the production of cytokines by a selected T helper cell 3. Differentiation of the selected B cell into plasma cells and B memory cells 4. Production and release of antibodies to defend against a specific pathogen
58
cell-mediated immunity 
an adaptive immune response in which infected or abnormal cells are destroyed by cytotoxic T cells. 1. Antigen-presenting cells come upon a naive T cell with a T cell receptor that matches the antigen being presented, initiating clonal selection. When this occurs, the naive T cell becomes selected and is stimulated by cytokines released by the selected T helper cell to undergo clonal expansion and differentiation. 2. The clones of the selected T cell differentiate into cytotoxic T cells and T memory cells. T memory cells are copies of the originally selected T cell that reside in the body for extended periods of time and help form immunological memory. The majority of selected T cells differentiate into cytotoxic T cells, which leave the lymph node and travel throughout the body, eventually reaching the site of infection. 3. Due to clonal selection, the cytotoxic T cells that arrive at the site of infection all have T cell receptors that are specific to the foreign antigen selected for. Once the cytotoxic T cell has found an abnormal cell that is presenting complementary foreign antigens on its MHC I complex, it binds to it. Chemicals, such as perforin, are then secreted by the cytotoxic T cell to induce apoptosis in the cell
59
B lymphocyte 
a type of lymphocyte that plays an important role in humoral immunity and differentiates into plasma cells and B memory cells
60
cytokine 
a signalling molecule released by cells (typically in the immune system) which aids in communication between immune cells and helps protect against pathogens
61
clonal expansion 
the process in which many copies of a lymphocyte are generated
62
clonal selection 
the process in which B and T cells encounter an antigen that matches their antigen binding site, and then generate many copies of themselves
63
differentiation 
the process in which cells develop specialised characteristics, typically transforming them from one cell type to another more specialised cell type
64
B memory cell 
a differentiated B lymphocyte that is responsible for providing long-lasting immunological memory of an antigen
65
plasma cell
a differentiated B lymphocyte that is responsible for the generation and secretion of antibodies during the humoral response
66
Steps in the humoral immune response
1. Selection of a B cell 2. Stimulation of the selected B cell through the production of cytokines by a selected T helper cell 3. Differentiation of the selected B cell into plasma cells and B memory cells 4. Production and release of antibodies to defend against a specific pathogen
67
disulphide bond 
a strong covalent bond occurring between two sulphur atoms
68
Neutralisation
Antibodies can block the sites of pathogens that are used to attack host cells (e.g. the site used by a virus to enter a cell) and can block the active sites of toxins.
69
Agglutination
Antibodies can bind together with antigens on two separate pathogens, forming large antigen-antibody complexes. This makes it easier for phagocytes to recognise the pathogens as foreign bodies and destroy them.
70
Immobilisation
Antibodies can also restrict the movement of pathogens around the body through the formation of large antigenantibody complexes.
71
Opsonisation
Antibodies can bind directly to the surface of a pathogen to make it easier to phagocytose
72
Activation of complement proteins
Antibodies attached to the surface of pathogens can facilitate the actions of complement proteins, including the formation of membrane attack complexes (MACs).
73
cytotoxic T cell (Tc) 
a differentiated T lymphocyte that is responsible for the destruction of infected or abnormal cells
74
T memory cell 
a differentiated T lymphocyte that is responsible for providing long-lasting immunological memory
75
apoptosis 
the controlled death of cells in the body. Also known as programmed cell death

Biology (13 decks)

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