4.1 Flashcards
(256 cards)
1
Q
I have not included all the ‘did you know’ boxes in this deck.
A
😉
2
Q
What is the organism in which a pathogen lives called?
A
The host.
3
Q
What does a host body create for a pathogen?
A
A good habit in which microorganism can live.
4
Q
What is a pathogen?
A
A microorganism that causes disease.
5
Q
How do pathogens live?
A
By taking nutrition from their host, but also cause damage in the process. This damage can be considerable.
6
Q
Where do numerous types of microorganism live in or on?
A
The body of another organism.
7
Q
What kingdom does bacteria belong to?
A
The kingdom Prokaryoate.
8
Q
How does the size of eukaryotic cell’s compare bacteria cells?
A
Bacteria cells are smaller than eukaryotic cells.
9
Q
How often do bacteria reproduce?
A
In the right conditions, some types of bacteria can reproduce every 20 minutes. Once in the hosts body, they can multiply rapidly.
10
Q
What can the presence of bacteria cause?
A
Their presence can cause diasease by damaging cells or by releasing waste products and/or toxins that are toxic to the host. In plants, the bacteria often live in the vascular tissues and cause blackening and death of these tissues .
11
Q
What are the problems caused by fungi?
A
Fungi can also cause a variety of diseases in both plants and animals. There are common fungal infections where the fungus lives in the skin of an animal, and where its hyphae, which form a mycelium, grow under the skin surface.
12
Q
How does fungi grow across the skin surface?
A
The fungus can send out specialised reproductive hyphae, which grow to the surface of the skin to release spores. This causes redness and irritation.
13
Q
Where do fungi live in pants?
A
In plants, the fungus often lives in the vascular tissue, where it can gain nutrients.
14
Q
What do fungi cause in a plant?
A
The hyphae release extracellular enzymes, such as cellulases, to digest the surrounding tissue, which causes decay. Leaves will often become mottled in colour, curl up and shrivel, before dying. Fruit and storage organs, such as tubers (potatoes) will turn black and decay.
15
Q
How do viruses reproduce?
A
Viruses invade cells and take over the genetic machinery and other organelles of the cell. They then cause the cell to manufacture more copies of the virus. The host cell eventually bursts, releasing many new viruses which will infect healthy cells.
16
Q
Describe protoctista.
A
There are a number of diseases caused by animal-like protoctists. These organisms usually cause harm by entering host cells and feeding on the contents as they grow.
17
Q
What parasite feeds on haemoglobin inside red blood cells?
A
The malarial parasite Plasmodium has immature forms that feed on the haemoglobin inside red blood cells.
18
Q
What are the characteristics of tuberculosis?
A
A disease that affects many parts of the body killing the cells and tissues: the lungs are most often affected.
19
Q
What is the organism that causes tuberculosis?
A
Bacteria Mycobacterium tuberculosis and M. bovis
20
Q
What are the characteristics of bacterial meningitis?
A
Infection of the meninges - the membranes that surround the brain and spinal cord; the membranes become swollen and may cause damage to the brain or nerves
21
Q
What is the organism that causes bacterial meningitis?
A
bacteria Neisseria meningitidis or Streptococcus
22
Q
What are the characteristics of ring rot (in plants) ?
A
Ring decay in the vascular tissue of a potato tuber or tomato, accompanied by leaf wilting.
23
Q
What is the organism that causes ring rot (in plants) ?
A
bacterium Clavibacter michiganensis subsp. sepedonicus
24
Q
What are the characteristics of HIV/AIDS?
A
attacks cells in the immune system and comprises the immune response.
25
What is the organism that causes HIV/AIDS?
virus; human immunodeficiency virus
26
What are the characteristics of influenza?
attacks respiratory system and causes muscle pains and headaches.
27
What is the organism that causes influenza?
virus from family Orthomyxoviridae - 'flu' viruses
28
What are the characteristics of tobacco mosaic virus?
causes mottling and discolouration of leaves.
29
What is the organism that causes tobacco mosaic virus?
virus tobacco mosaic virus.
30
What are the characteristics of black sigatoka (bananas)?
causes leaf spots on banana plants reducing yield
31
What is the organism that causes black sigatoka (bananas)?
fungus Mycosphaerella fijiensis
32
What are the characteristics of blight (tomatoes and potatoes) ?
affects both leaves and potato tubers
33
What is the organism that causes blight (tomatoes and potatoes) ?
protoctistan phytophthora infestans
34
What are the characteristics of ringworm (cattle)?
growth under skin of feet - particularly between the toes
35
What is the organism that causes ringworm (cattle)?
fungus Trichophyton rubrum
36
What are the characteristics of athlete's foot (humans)/
growth under skin of feet - particularly between the toes
37
What is the organism that causes athlete's foot (humans)/
fungus Trichophyton rubrum
38
What are the characteristics of malaria?
parasite in the blood that causes headache and fever and may progress to coma and death.
39
What is the organism that causes malaria?
protoctistan Plasmodium falciparum, P. vivax, P. ovale, P. malariae
40
Give an example of a organism that causes diasease that is hard to classify.
Phytophthora (blight) has been classified as a fungus for many years. Recently, it was moved to the kingdom Protoctista, before being placed in a new kingdom (stramenopila), because it has many features that do not fit with other fungi (it does not fit the mould).
41
What is direct transmission?
passing a pathogen from host to new host, with no intermediary.
42
What is indirect transmission?
passing a pathogen from host to a new host, via a vector.
43
What is a vector?
an organism that carries a pathogen from one host to another.
44
What is transmission?
passing a pathogen from an infected individual to an uninfected individual. (remember it is the pathogen that is transmitted not he disease)
45
Pathogens have life cycles that involves living in or on other living things. What is the by-product of this life cycle?
That they cause harm to their host.
46
What are the stages of the life cycle of a pathogen?
Travel from one host to another (transmission) entering the host's tissues reproducing leaving the hosts tissues
47
Pathogenic organisms can be transmitted between animals in a variety of ways, which is the most common?
direct transmission.
48
What are the different methods of transmission?
Direct physical contact, faecal - oral transmission, droplet infection and transmission by spores.
49
Describe direct physical contact as a means of transmission.
such as touching a person who is infected or touching contaminated surfaces (including soil) that harbour the pathogens.
50
What are some examples of diseases caught through direct physical contact?
For example, HIV, bacterial meningitis, ringworm, athlete's foot.
51
What are factors that cause transmission through direct physical contact?
Hygiene: washing hands regularly - especially after using the toilet. Keeping surfaces clean - especially door handles. Cleaning and disinfecting cuts and abrasions. Sterilising surgical instruments. Unsing condoms during sexual intercurse.
52
Describe faecal - oral transmission as a means of transmission.
usually by eating food or drinking water contaminated by the pathogen.
53
What are some examples of diseases caught through faecal - oral transmission?
For example, cholera and food poisoning.
54
What are factors that cause transmission through faecal - oral transmission?
Using human sewage to fertilise crops is a common practice in some parts of the world. Treatment of waste water and treatment of drinking water are important ways to reduce the risk. Thorough washing of all fresh food (using treated water). Careful preparation and thorough cooking of all food.
55
Describe droplet infection as a means of transmission.
in which the pathogen is carried in tiny water droplets in the air.
56
What are some examples of diseases caught through droplet infection?
tuberculosis and influenza
57
What are factors that affect transmission through droplet infection?
Catch it - bin it - kill it. Cover your mouth when coughing or sneezing. Use a tissue and ensure the tissue is disposed of correctly.
58
Describe transmission by spores as a means of transmission.
Transmission by spores, which are a resistant stage of the pathogen. These can be carried in the air or reside on surfaces or in the soil.
59
What are some examples of diseases caught through transmission of spores?
anthrax and tetanus
60
What are factors that affect transmission through transmission of spores?
Use of mask. Washing skin after contact with soil.
61
What social factors affect transmission of a pathogen?
Overcrowding - many people living and sleeping together in one house. poor ventilation poor health - particularly if a person has HIV/AIDS, as they are more likely to contract other diseases poor diet homelessness living or working with people who have migrated form areas where a disease is more common.
62
How are diseases transmitted indirectly?
Via a vector. A vector is another organism that may be used by the pathogen to gain entry to the primary host.
63
Use malaria to give an example of indirect transmission.
For example, the Plasmodium parasite that causes malaria enters the human host via a bite from a female Anopheles mosquito. The life cycle of Plasmodium, which uses a vector
64
What is the life cycle of Plasmodium?
-\> a person with malaria -\> gametes of plasmodium in blood -\> female mosquito sucks blood -\> plasmodium develops and migrates to a mosquito's salivary glands -\> an uninfected person is bitten -\> PLasmodium migrates to the liver -\> PLasmodium migrates to the blood -\>
65
How can plant pathogens be spread?
Plant pathogens can also be spread by direct and indirect means. Many pathogens are present in the soil and will infect plants by entering the roots - especially if these havent
66
How does fungi reproduce?
Many fungi produce spores as a means of sexual or asexual reproduction. These spores may be carried in the wind - airborne transmission.
67
What course of action does the pathogen take when inside a plant?
Once a pathogen is inside the plant, it may affect all the vascular tissue.
68
How do pathogens spread?
Pathogens in the leaves are distributed when the leaves are shed and carry the pathogen back to the soil where it can grow and infect another plant/ Pathogens can also enter fruit and seeds, and will the be distributed with the seeds - so that many or all the offspring are infected.
69
Describe how indirect transmission often occurs in plants.
Indirect transmission of plant pathogens often occurs as a result of insect attack. Spores or bacteria become attached to a burrowing insect, such as a beetle, which attacks an infected plant. When that beetle attacks another plant, the pathogen is transmitted to the uninfected plant. The beetle is acting as a vector. For example, the fungus that causes Dutch elm disease is carried by the beetle Scolytus multistriatus.
70
In what climates are protoctists most common?
Many protoctists, bacteria and fungi grow and reproduce more rapidly in warm and moist conditions. Therefore they tend to be more common in warmer climates.
71
Why are protoctists most common in warm climates?
In cooler climates, these pathogens may be damaged or even killed by cold winter weather - such weather will reduce their ability to grow and reproduce. As a result, there is a greater variety of diseases to be found in warmer climates, and animals or plants living in these regions are more likely to become infected.
72
What is making Europe more appealing to pathogens?
As Global warming alters our climate, these pathogens will be able to survive more easily in Europe. Tropical diseases may become more common in Europe as a result.
73
What is callose?
a large polysaccharide deposits that blocks old phloem sieve tubes.
74
Plants manufacture sugars in photosynthesis and convert those sugars to a wide range of compounds such as proteins and oils. Therefore what does it represent to a pathogen?
Therefore they represent a rich scource of nutrients for many organisms such as bacteria, fungi, protoctists and viruses may be pathogenic.
75
What do plants have as an immune system?
Plants do not have an immune system comparable with animals. But they have developed a wide range of structural, chemical and protien-based defences which can detect invading organisms and prevent them from causing extensive damage. This includes both passive defences to prevent entry and active defences which are introduced when the pathogen is detected.
76
What is a passive defence?
These are defences present before infection, and their role is to prevent entry and spread of the pathogen. Passive defences include physical barriers and chemicals.
77
Why are the physical defences of a plant against pathogens?
cellulose cell wall, lignin thickening of cell walls, waxy cuticles, bark, stomatal closure, callose and tylose
78
Describe cellulose cell wall as a physical plant defence against pathogens.
this not only acts as a physical barrier but most plant cell walls contain a variety of chemical defences that can be activated when a pathogen is detected.
79
Describe lignin thickening of cell walls as a physical plant defence against pathogens.
lignin (a phenolic compound) is waterproof and almost completely indigestible.
80
Describe as a physical plant defence against pathogens.
these prevent water collecting on the cell surfaces. Since pathogens collect water and need water to survive, the absence of water is a passive defence.
81
Describe waxy cuticles as a physical plant defence against pathogens.
these prevent water collecting on the cell surfaces. Since pathogens collect in water and need water water to survive, the absence of water is a passive defence.
82
Describe bark as a physical plant defence against pathogens.
most bark contains a variety of chemical defences that work against pathogenic organisms.
83
Describe stomatal closure as a physical plant defence against pathogens.
stomata are possibly points of entry pathogens. Stomatal aperture is controlled by the guard cells. When pathogenic organisms are detected, the guard cells will close the stomata in that part of the plant.
84
Describe callose as a physical plant defence against pathogens.
callose is a large polysaccharide that is deposited in the sieve tubes at the end of growing season. It is deposited around the sieve tubes and blocks the flow in the sieve tube. This can prevent a pathogen spreading around the plant.
85
Describe tylose as a physical plant defence against pathogens.
a tylose is a balloon-like swelling or projection that fills the xylem vessel. When a tylose is fully formed, it plugs the vessel and the vessel can no longer carry water. Blocking the xylem vessel prevents spread of pathogens through the heartwood. The tylose contains a high concentration of chemicals such as terpenes that are toxic to pathogens.
86
When chemical deferences do plant tissues contain?
Plant tissues contain a variety of chemicals that have anti-pathogenic properties. These include terpenoids, phenols, alkaloids and hydrolytic enzymes.
87
When are chemical defences used within plant tissue?
Some of these chemicals, such as terpenes in tyloses and tannins in bark, are present before infection. However, because the production production of chemicals require a lot of energy, many chemicals are not produced until the plant detects an infection.
88
How does a plant know a pathogen is attacking?
When a pathogen attacks, specific chemicals in their cell walls can be detected by the plant cells. These chemicals include specific proteins and glycolipids.
89
How does a plant respond to attack of pathogens?
The plant responds by fortifying the defences already present. This includes increasing the physical defences and producing defensive chemicals.
90
What are the active defences of a plant?
Cell walls become thickened and strengthened with additional cellulose. Deposition of callose between the plant cells wall and cell membrane near the invading pathogen. Oxidative bursts that produce highly reactive oxygen molecules capable of damaging the cells of invading organisms. An increase in production of chemicals.
91
Active defences; What is the action of the chemical terpeniods?
A range of essential oils that have antibacterial and antifungal properties. They may also create scent, for example, the menthols and menthones produced by mint plants.
92
Active defences; What is the action of the chemical phenols?
These have antibiotic and antifungal properties. Tannins found in bark inhibit attack by insects. These compounds bond to salivary proteins and digestive enzymes such as trypsin and chymotrypsin, deactivating the enzymes. Insects that ingest high amounts of tannins do not grow and will eventually die. This helps to prevent the transmission of pathogens.
93
Active defences; What is the action of the chemical alkaloids?
Nitrogen-containing compounds such as caffeine, nicotine, cocaine, morphine, solanine. These give a bitter taste to inhibit herbivores feeding. They also act on a variety of metabolic reactions via inhibiting or activating enzyme action. Some alkaloids inhibit proton synthesis. If the plant can reduce grazing by larger animals, then it will suffer less damage that can allow pathogens to enter the plant.
94
Active defences; What is the action of the chemical defensive proteins (defensins)?
These are small cysteine-rich proteins that have broad anti-microbial activity. They appear to act upon molecules in the plasma membrane of pathogens, possibly inhibiting the action of ion transport channels.
95
Active defences; What is the action of the chemical hydrolytic enzymes?
These are found in the spaces between cells. They include chitinases (which break down the chitin found in fungal cell walls), glucanases (which hydrolyse the glycosidic in glucans) and lysozymes (which are capable of degrading bacterial cell walls.
96
What is necrosis?
Deliberate cell suicide. A few cells are sacrificed to save the rest of the plant.
97
Why do plant cells undergo necrosis?
By killing cells surrounding the infection, the plant can limit the pathogens access to water and nutrients and can therefore stop it spreading further around the plant.
98
How is cell suicide activated?
Necrosis is brought about by intracellular enzymes that are activated by injury. These enzymes destroy damaged cells and produce brown spots on leaves or dieback.
99
What is a canker?
A sunken necrotic lesion in the woods tissue such as the main stem or branch. It causes death of the cambium tissue in bark.
100
What is inflammation?
Swelling and redness of tissue caused by infection.
101
What is a mucous membrane?
Specialised epithelial tissue that is covered by mucous.
102
What are primary defences?
Those that prevent pathogens entering the body.
103
What do primary defences defend against?
Pathogenic organisms need to enter the body of their host before they can cause harm. Evolution has selected hosts adapted to defend themselves against such invasions. The mechanisms that have evolved to prevent entry of pathogenic organisms are called primary defence. They are non-specific, as they will prevent the entry of any pathogen.
104
What is the body's main primary defence?
The body is covered by the skin. This is the main primary defence.
105
What is the outer layer of the skin called?
The epidermis and it consists of layers of cells.
106
What at most of the cells in the epidermis of skin called?
Keratinocytes
107
How are the skin keratinocytes cells formed?
These cell are produced by mitosis at the base of the epidermis. They then migrate out to the surface of the skin. As they migrate, they dry out and the cytoplasm is replaced by the protein keratin. This process is called keratinisation, and it takes about 30 days. By the time that the cells reach the surface they are no longer alive. The keratinised layer of dead cells acts as an effective barrier to pathogens. Eventually, the dead cells slough off.
108
The skin is only protective when its complete, how does the body respond to abrasions or lacerations to the skin which opens the body to infection?
The body must prevent excess blood loss by forming a clot, making a temporary seal to prevent an infection, and preparing the skin.
109
Describe blood clotting.
Blood clotting is a complex process, as it is important to prevent clots forming in blood vessels when they are not needed. It involves calcium ions and at least 12 factors - known as clotting factors. Many of the clotting factors are released from platelets and form the damages tissue. These factors activate an enzyme cascade.
110
How is the temporary seal formed over a wound site?
Once the clot has formed, it begins to dry out and form a scab. The scab shrinks as it dries, drawing the sides of the cut together. This makes a temporary seal under which the skin is repaired.
111
What is the first stage of repairing the skin after a seal has been made?
The first stage is the deposition of fibrous collagen under the scab.
112
When repairing the skin what is the stage ofter deposition?
Stem cells in the epidermis then divide by mitosis to form new cells, which migrate to the edges of the cut and differentiate to form new skin.
113
What are the final stages of repairing skin after the skin stem cells have differentiated?
New blood vessels grow to supply oxygen and nutrients the the new tissues. The tissues contract to help draw the edges of a cut together so that the repair can be completed, the scab will be released.
114
Flow diagram - pg 235 What will damage to blood vessel wall, exposing collagen and releasing clotting factors cause?
Platelets bind to collagen and release clotting factors and an inactive thrombokinase in blood (factor X), will become and active thrombokinase (an enzyme).
115
Flow diagram - pg 235 How will an active thrombokinase form a clot?
With the addition of prothrombin in the blood and calcium ions (Ca2+) an active thrombin will form (an enzyme). This with the addition of soluble fibrinogen in plasma will form insoluble fibrin. These fibres attach to platelets in the plug and form a plug along with red blood cells and platelets trapped and a temporary platelet plug formed.
116
Flow diagram - pg 235 How is a temporary platelet plug formed?
Damage to the blood vessel wall exposes collagen and releases clotting factors, this causes platelets to bind to collagen and release clotting factors ( as well as activate thrombokinase ) which will form a temporary platelet plug and help to form the clot.
117
Certain substances, such as oxygen and the nutrients in our food, must enter our blood. What problems does this cause to our boys defence system?
The exchange surfaces where this occurs must be thinner and are less well protected from pathogens. The air and food we take in form our environment may harbour microorganisms. Therefore, the airways, lungs and the digestive system are at risk of infection.
118
What are the key components of a mucous membrane?
Bacteria trapped in mucous, mucous, cilia that move the mucous, goblet cells and mucous secreting hands. (diagram on page 235)
119
What areas are protected by mucous membranes?
The airways, lungs and the digestive system.
120
What does the epithelial layer of mucous membrane contain?
The epithelial layer contains mucous-secreting cells called goblet cells. There are also extra mucous-secreting glands under the epithelium.
121
What is the purpose of mucous and where is it found?
In the airways, the mucous lines the passages and traps any pathogens that may be in the air. Mucous membranes are also found in the gut, genital areas, anus, ears and nose.
122
How is the mucous removed?
The epithelium also has ciliated cells. The cilia are tiny, hair like organelles that can move. They move in a co-ordinated fashion to waft the layer of mucous along. They move the mucous up to the top of the trachea, where it can enter the oesophagus. It is swallowed and passes down the digestive system.
123
How are the pathogens transported by mucous killed?
Most pathogens in the digestive system are killed by the acidity of the stomach, which can be pH 1-2. This denatures the pathogens enzymes.
124
What causes coughing and sneezing?
Areas that are prone to attack are also sensitive. They respond to the irritation that may be caused by the presence of micro-organisms or the toxins they release. These reflexes include coughing sneezing and vomiting. in a cough or sneeze the sudden expulsion of air will carry with it the microorganisms causing the irritation.
125
One of the signs that a tissue is infected is swelling and redness known as inflammation. How may this feel?
hot and painful
126
What is the cell signalling substance that causes inflammation?
The presence of microorganisms in the tissue is detected by specialised cells called mast cells. These cells release a cell signaling substance called histamine. Histamine has a range of effects on the surrounding tissue, which act to help combat the infection.
127
What is the effect of Histamine?
The main effect is to cause vasodilation and make capillary the walls more permeable to white blood cells and some proteins. Blood plasma and phagocytic white blood cells leave the blood and enter the tissue fluid. This leads to increased production of tissue fluid, which causes the swelling (oedema).
128
Where is excess tissue fluid drained in the inflammation of an infected tissue?
Excess tissue fluid is drained into the lymphatic system where lymphocytes are stored. This can lead to the pathogens coming into contact with the lymphocytes and initiating specific immune response.
129
Name the primary defences against disease.
the skin, blood clotting and skin repair, mucous, membranes, coughing and sneezing, inflammation the eyes are protected by antibodies and enzymes in tear fluid. The ear canal is lined by wax, which traps pathogens. The female reproductive system is protected by a mucous plug in the cervix and by maintaining relatively acidic conditions in the vagina.
130
What is a antigen-presenting cell?
a cell that isolates the antigen from a pathogen and places it on the plasma membrane so that itcan be recognised by other cells in the immune system.
131
What is a antigen-presenting cell?
A cell that isolates the antigen from a pathogen and places it on the plasma membrane so that it can be recognised by other cells in the immune system.
132
Clonal selection
Selection of a specific B or T cell that is specific to the antigen.
133
What is clonal selection?
Selection of a specific B or T cell that is specific to the antigen.
134
Cytokines
Hormone-like molecules used in cell signalling to stimulate the immune response.
135
What is a neutrophil?
A type of white blood cell that engulfs foreign matter and traps it in a large vacuole (phagosome), which fuses which lysosomes to digest the foreign matter.
136
What are opsonins?
Proteins that bind to the antigen on a pathogen and then allow phagocytes to bind.
137
What are secondary defences used for?
To combat pathogens that have entered the body.
138
What allows the body to recognise a pathogen?
When a pathogen invades the body, it is recognised as foreign by chemical markers on its outer membrane. These markers are called antigens. They are proteins or glycoproteins intrinsic to the plasma membrane.
139
What are opsonins?
Are origins molecules that attach to the antigens on the surface if a pathogen. They are a type of antibody.
140
What is the role of opsonins?
The role of the opsonin is to enhance the ability of phagocytic cells to bind and engulf the pathogen. Some opsonins are not very specific - so that they can attach to a variety of pathogenic cells.
141
What is the first line of secondary defence against a pathogen?
Phagocytosis, specialised cells in the blood and tissue fluid engulf and digests the pathogen.
142
What are the most common phagocytes?
Neutrophils, you can recognise these cells by their multi-lobed nucleus.
143
Where are neutrophils manufactured?
In the bone marrow.
144
Where and when are neutrophils found?
They travel in the blood and often squeeze out of the blood into tissue fluid. Neutrophils are short-lived, but they will be released in large numbers as a result of an infection.
145
How do neutrophils get rid of the pathogen?
Neutrophils contain a large number of lysosomes, they engulf and digest pathogens, neutrophils usually die soon after digesting a few pathogens. Dead neutrophils may collect in an area of infection, to form pus.
146
Describe in four stages a neutrophil digesting a pathogen.
Neutrophil binds to the opsonin attached to the antigen of the pathogen. The pathogen is engulfed by endocytosis forming a phagosome. Lysosomes fuse to the pathogen and release lytic enzymes into it. After digestion, the harmless products can be absorbed into the cell.
147
Table that needs to be revised - pg 240. What is the purpose of T-Killer cells?
T killer cells attack infected host cells.
148
What is the purpose of T memory cells?
T memory cells remain in the blood.
149
What is the purpose of T helper cells?
To stimulate B cells to divide.
150
What is the purpose of plasma cells?
Plasma cells make antibodies.
151
What is the purpose of B memory cells?
B memory cells remain in the blood.
152
How is the immune response triggered?
An invading pathogen has specific antigens. In order to trigger the immune response, these must be detected by T and B lymphocytes that carry the specific receptor molecules on their plasma membranes. The receptor molecules are proteins that have a shape that is complimentary to the shape of the antigen.
153
When can contact between the antigen and lymphocytes be achieved?
It can be achieved directly when pathogenic cells enter the lymph nodes or by the action of antigen-presenting cells.
154
What happens in clonal expansion (proliferation)?
Once the correct lymphocytes have been activated they must increase in numbers to become effective. This is achieved by mitotic cell division.
155
What happens in the differentiation of the specific immune response system?
The B and T lymphocytes do not manufacture the antibodies directly. Once selected, clones of the lymphocytes develop into a range of useful cells.
156
What are agglutinins?
Antibodies that cause pathogens to stick together.
157
What are anti-toxins?
Antibodies that render toxins harmless.
158
What are opsonins?
Antibodies that make it easier for phagocytes to engulf the pathogen.
159
What is a primary immune response?
The initial response caused by a first infection.
160
What is a secondary immune response?
A more rapid and vigorous response caused by a second or subsequent infection by the same pathogen.
161
What type of molecule can act as a antigen?
Antigens are molecules that can stimulate immune response. Almost any molecule can act as an antigen, but they are usually proteins o glycoproteins in the plasma membrane of the pathogen.
162
What will stimulate the production of antibodies?
A foreign antigen will be detected by the immune system and will stimulate the production of antibodies.
163
Why do our own antigens not trigger immune response?
Antibodies are specific to the antigen. As the antigen is specific to the organism, we can think of the antibody as being specific to the pathogen. Our own antigens are recognised by our immune system and do not usually stimulate any response.
164
Why are antibodies immunoglobulins?
They are complex proteins produced by the plasma cell in the immune system. They are released in response to an infection. They have a region with a specific shape that is comlimentary to that of a particular antigen.
165
When must our immune system manufacture antibodies?
Our immune system must manufacture one type of antibody for every antigen that is detected. Antibodies attach to antigens and render them harmless.
166
What are immunoglobulins?
Immunoglobulins, also known as antibodies, are glycoprotein molecules produced by plasma cells (white blood cells). They act as a critical part of the immune response by specifically recognizing and binding to particular antigens, such as bacteria or viruses and aiding in their destruction.
167
What shape are antibodies?
Antibody molecules are Y-shaped and have two distinct regions.
168
What does an antibody consist of?
They consist of four polypeptide chains, a light polypeptide chain and a heavy polypeptide chain. Disulphide bridge to hold polypeptides together. A hinge region to allow flexibility so molecule can grip more than one antigen. (diagram pg241)
169
Describe the two regions of an antibody.
A variable region, which has a shape specific to the shape of the antigen. A constant region which is all the ska in all antibodies - it may have a site for the easy binding of phagocytic cells.
170
Antibodies work in a variety of ways, but most act by ataching to the antigens on a pathogen, what are the three main types of antibodies?
Opsonins, agglutinins, and anti-toxins.
171
What are opsonins?
Opsonins are a group of antibodies that bind to the antigens on a pathogen. They then act as binding sites for phagocytic cells, so that these can more easily bind and destroy the pathogen.
172
What are how do opsonins vary?
Some opsonins are not very specific and stick to types of molecules that are not found in the host cell, e.g. the peptidoglycans found in the cell walls of bacteria. Other opsonins are produced as part of the specific immune response and bind to very specific antigens. The pathogen may have another use for this antigen molecule .
173
Give an example of an opsonin which is part of the specific immune response, when the pathogen has another use for the antigen molecule the opposition is binding to.
It may be a binding site used for attachment to the host cell. In this case, the opsonin bound to the antigen renders the antigen useless - a process known as neutralisation. The opsonin assists in phagocytosis, but also prevents the pathogen entering a host cell before it can be attacked by phagoctyes.
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What are agglutinins?
Because each antibody has two identical binding sites it is able to 'crosslink' pathogens by binding an antigen on one pathogen with one binding site and then an antigen on another pathogen with its other binding site. When many antibodies perform this cross linking they clump together (agglutinate) pathogens.
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What are the advantages of agglutinins clumping together pathogens? (agglutinate)
The agglutinated pathogens are physically impeded from carrying out some functions, such as entering host cells, and the agglutinated pathogens are readily engulfed by phagocytes. This is particular affective against viruses.
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What are anti-toxins?
Some anti-bodies bind to molecules that are released by pathogenic cells. These molecules may be toxic and the action of anti-toxins renders them harmless.
177
Describe opsonisation in four stages.
An antibody molecules has two binding sites. It also has an end that can stimulate phagocytosis. A pathogen has several antigens on its surface. The antibody binds to the antigen, and the pathogen is engulfed by a phagocyte and the end of the antibody stimulates phagocytosis.
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What are agglutinated pathogens?
Non-infective and easily phagocytosed.
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What is a macrophage?
Macrophages are larger cells manufactured ion the bone marrow. They travel in the blood as monocytes (look at the picture) before settling in the body tissues.
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Where are many monoctes found?
Many are found in the lymph nodes where they mature into macrophages.
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What is the role of macrophages?
Macrophages paly an important role in initiatng the specific responses to invading pathogens.
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What does a macrophage do when it englufs a pathogen?
183
Describe the role of an antigen presenting cell?
184
What is the activation of specific B and T cells called?
**colonal selection**
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What does the activation of B and T cells, **clonal selection** cause?
This brings into play a complex series of events that leads to the production of antibodies that can combat the specific pathogen and memory cells that will provide long-term immunity.
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What is the series of events activated by colonal selction stimulated and co-ordinated by?
a number of hormone-like chemicals called **cytokines**. These stimulate the diferentiation and activity of macropahges, B cells and T cells.
187
Describe an investigation looking at blood cells.
* Blood cells can be viewed in a blood smear.
* A thin layer of blood is spread out o a slide, and is stained to make the white blood cells more visible.
* The red blood cells are pink in colour.
* Note that red blood cells do not always look like a perfect bioconcave disc.
* Monocytes are the largest white blood cells and usually have a large kidney shaped nucleus.
* Neutrophils have a multilobed nucleus. Lymphocytes are smaller, and the nucleus alomost fills the cell.
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What are antibodies?
specific protiens released by plasma cells that can attach to pathogenic antigens.
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What are B memory cells?
Cells that remain in the blood for a long time, providing long term immunity.
190
Whta is colonal exapansion?
An increase in the number of cells by mitotic cell division.
191
What are interleukins?
Signalling molecules that are used to communiacte between different white blood cells.
192
What are plasma cells?
derived from B lymphocytes, these are cells that manufacture antibodies.
193
What are T helper cells?
cells that release signalling molcules to stimulate the immune response
194
What are T killer cells?
cells that attack and destroy our own body vells that are infected by a pathogen.
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What are T memory cells?
cells that remain in blood for a long time, providing long-term immunity.
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What are T regulator cells?
cells that are involved with inhibiting or ending the immune repsonse.
197
What does the specific immune response involve?
The speciifc immune response involves B lymphocytes (B cells) and T lymphocytes (T cells). These are white blood cells with a large nucleus and specialised receptors on their plasma membranes (cells surface membranes).
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What does the immune repsonse provides?
Ther immune response produces **antibodies.** It is the antibodies that actually neutralise the foreign antigens. The immune response provides long-term protection from the disease. It produces immunological memory through release of memory cells, which circulate in the body for a number of years.
199
What cells do T lymphocytes develop or differentiate into?
1. T helper cells (Th)
2. T killer cells (Tk)
3. T memory cells (Tm)
4. T regulator cells (Tr)
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What is the purpose of T helper cells (Th)?
To release cytokines (chemical messengers) that stimulate the B cells to develop nad stimulate pahgocytosis by the phagocytes.
201
What is the purpose of T killer cells (Tk)?
To attack an dkill host-body cells that dsplay foreign the antigen.
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What si the purpose of T memory cells (Tm)?
To provide long term immunity.
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What is the purpose of T regulator cells (Tr)?
To shut down the immune response after the pathogen has been suscessfully removed. They are also involved in preventing autoimmunity.
204
What cells do B lymphocytes (**B** **cells)** develop into?
1. Plama cells
2. B memory cells (Bm)
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What is the purpose of Plasma cells?
To circulate in the blood, manufacturing and releasing the antibodies.
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What is the purpose of B memory cels (Bm)?
To remain in the body for a number of years and act as the immunological memory.
207
Thye specifc immune response involves the co-ordinated action of a range of cells. In order to work togther effectively they need to communicate, this is known as cell signalling. How is this communication achieved?
208
Give three examples of communication using cytokines.
209
What occurs when the immune system attacks a part of the body?
An autoimmune disease.
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How is autoimmune disease usually prevented within the body?
Normallly an B or T cells that are specific to our own antigens are destroyed during ear4ly development of the immune system.
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When does an autoimmune disease arise?
When antibodies start to attack our own antigens - possibly because antigens that are not normally exposed become exposed to attack.
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The causes of autoimmune disease are unknown, but seem to include both genetic and environmental factors. What are some examples?
* Artritus is a painful inflammation of a joint. The cause is uncertain, but it starts with antibodies attacking the membrane around the joint.
* Lupus can affect any part of the body, causing swelling and pain. It may be associated with antibodies that attack certain portions in the nucleus in cells and affected tissues.
213
How would a plasma cell be specialised?
They will contain numerous organelles associated with protien synthesis and secretion.
* Numerous ribosmes
* a lot of rough ER
* a lot of Golgi apparatus
* numerous mitrochondria
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What is the primary immune response?
Antibodies are priduced in response to infection. When an infecting agent is forst detected, the immune systrem starts to produce antiboies. But it takes a few days the number of antibodies in the blood rises to a level that cancombat the infection successfully. Tis is known as the **primary immune repsonse.**
215
What happens to the antibodies when the pathogen has been dealth with?
The number of antibodies in the blood drops raidly.
216
Describe the secondary immune system.
Antibodies do not stay in the blood. If the body is infected a second time by the same pathogen the antibodies must be made agian. There will be B memory cells and T memory cells circulating in the blood, whicyh can recognise the specific antigens and the immune syste can swing into action more quickly. This time the production of antibodies starts sooner and is more rapid. So the concentration of antibosies rises sooner and reaches a higher concentration. This is know as the **secondary immune response** - it is usually qucick enough to prevent any symptoms being detected by the host.
217
Describe how the concentration of antibodies changes over time for primary and secondary immune responses.
218
What is active immunity?
Where the immune system is activated and manufactures its own antibodies.
219
What is artifical immunity?
immunity that is achieved as a result of medical intervention.
220
What is epidemic?
a rapid spread of dsease through a high proportion of the population.
221
What is natural immunity?
immunity achieved through normal life processes.
222
What is passive immunity?
immunity achieved when antibodies are passed to the individual through breast feeding or infection.
223
What is vaccination?
a way of stimulating an immune response so that immunity is achieved.
224
How does vaccination provide immunity to specific diseases?
The immunity is created by deliberate exposure to antigentic material that has been renderd harmless. The antigenic material is usually injected, but in some cases it can only be taken orally. The immune system treats the antigenic material as a real disease. As a result, the immune system is activated and manufacturesantibodies and memory cells. The memory cells provide long-term immunty.
225
What variety of forms can antigenic material used in vaccines take?
* Whole, live micro-organisms
* A harmless or attentuated (weakend) version of the pathogenic organisms (e.g. measels and TB vaccines).
* A dead pathogen (e.g. typoid and cholera vaccines).
* A preparation of the antigens from a pathogen (e.g. the hepatitus B vaccine).
* A toxoid, which is a harmless version of a toxin (e.g. the tetanus vaccine).
226
Describe the use of whole, live microorganisms as antigenic material in a vaccine.
Usually ones that are not as harmful as those that cause the real disease. But they must have very smilar antigens, so that the antibodies produced will be effecteive against the real pathogen (e.g. the smallpox vaccine, which uses a simular virus that causes cowpox).
227
Desacribe **herd immunity.**
**Herd immunity** is using a vaccine to provide immunity to all or almost all of the population at risk. Once enough people are immune, the disease can no longer be spread through the population and you achieve 'herd immunity'. In order to be effective, it is essential to vaccinate almost all the population.
228
Give two examples of the percenatge of people that needed be immunised to produce an effective herd vaccination.
To erradicate smallpox, it was necessary to vacinate 80-85% of the population. It is estimated that at least 95% of the population would need to be immunised in order to prevent the spread of measels.
229
In the UK what diseases does the vaccination programme to immunise young children cover?
1. Diphtheria
2. tetnus
3. whooping cough
4. polio
5. meningitis
6. measels
7. mumps
8. rubella.
These vaccines are given to the majourity of children at the appropiate age.
230
Describe **ring vaccination**.
**Ring vaccination** is used when a new case of a disease is reported. Ring vaccination involves vaccinating all the people in the immediate vicinity of the new cases(s). This may mean vaccinating the people in the surounding houses, or even in the whole village or town. Ring vaccination is also used in many parts of the world to controll the spread of livestock disease.
231
Discribe controll of epidemics in vaccination.
232
What are the dangers relaxing a routine vaccination?
233
Give an example of when an epidemic may occur.
Certain pathogen, such as the influenza virus, are relatively unstable and regularly undergo chnages in their antigens. When this occurs, and **epidemic** may arise.
234
Why must threats from epidemics be monitored?
Threats from epidemics must be monitored so that new strains of pathogens can be idnetified. This enables the health authorities to prepare for an impendig epidemic by stockpiling suitible vaccines and vaccinating people who are at particular risk from the disease.
235
What is influenzia?
(also known as flu) is a killer disease caused by a virus.
236
Who is most at risk from influenzia?
People over 65 years of age and those with respiratory tract conditions are particularly at risk.
237
Occasionally a new strain of virus arises that is particulay virulent. This may cause an epidemic, give an example of this.
In 1918 a flu epidemic killed at least 40 million people worldwide (some estimates are as high as 100 million). More recently, in 1968/69, about 1 million people were killed by Hong Kong Flu, also known as the H3N2 strain.
238
What is a very recent flu epidemic example?
In 2009-2010 about 540 000 cases of swine flu (H1N1) were reported to the UK. This strain of flu affected many people worldwide, but the exact numbers are uncertain, as the strain was less virulent than expected and many cases have gone unreported.
239
How does the UK attempt to avoid a worlwide epidemic (**a pandemic**)?
People at risk are immunised, in the UK, there is a vaccnination programme to immunise all those aged over 65 and those who are at risk for any other reason.
240
How did the UK try to immunise people in 2013-2014?
In 2013-2014, about 73% of people over the age of 65 were vaccinated, along with about 52% of younger people in at risk groups.
241
What is propsed in the UK to help immunise the population?
New versions of the influenzia vaccination have been developed which can be administered via a nasal spray. It is proposed that these will be offerd to all children in the upcoming years. The strains of flu used in this immunisation programme change each year. Worldwide reasearch is undertaken to determine which of the strains of flu are most likley to spread in any given year.
242
What are the different ways immunity can be achieved?
**Natural immunity** is achieved through normal life processes. **Artificial immunity** is achieved through medical intervention.
Immunity can be achieved actively or passively. **Active immunity** is achieved is achieved when the immune system is activated and manufactures its own antibodies. **Passive immunity** is achieved when the antibodies are supplied from another scource.
243
Describe active natural immunity.
Immunity provided by antibodies made in the immune system as a result of infection. A person suffers from the disease once and and then immune (e.g. immunity to chickenpox)
244
Describe active artifical immunty.
Immunity provided by antibodies made in the immune system as a result of vaccination. A person is injected with a weakened, dead or similar pathogen, or with antigens, and this activates his/her immune system (e.g. immunity to TB and influenza).
245
Describe natural passive immunity.
Antibodies provided via the placenta or via breast mil. This makes the baby immune to diseases to which the mother is immune. It is very useful in the first year of the babys life, when its immune system is developing.
246
Describe artificial immunity.
Immunity provided by injection of antibodies made by another individual (e.g. hepatitis A and B). Tetnus can also be treated this way when vaccination using a toxoid has not worked well.
247
What is an antibiotic?
A chemical which prevents growth of microorganisms. Antibiotics can be antibacterial or antifungal.
248
Personalised medicine
the development of designer medicines for individuals.
249
Whaty is synthetic biology?
the re-engineering of biology. This could be the production of new molecules that mimic natural processes, or the use of natural molecules to produce new biological systems that do not exist in nature.
250
How many drugs are currently availible in the UK?
There are currently over 6000 different kinds of medicine availible in the UK.
251
Why are new drugs needed?
* new diseases are emerging
* there are still many diseases for which there are no effective treatments
* some antibiotic treatments are becoming less effective
252
Who discovered the first antibiotic?
Alexander Fleming accidentally discovered antibiotic penicillin.
253
Who's work really demonstrated the potential value of antibiotics?
Florey and Chain, who purified penicillin. This shows how important it is for scientists to work togther.
254
Why have many drugs been used for centuries?
They are used because people have noticed that certain plants or extracts have a beneficial effect. The World Health Organisation calculates that 80% of the worlds population relies on traditional medicines.
255
Describe the use of traditional medicines in different cultures.
In India, some 7000 different plants are used for their medicinal properties, and in China they use about 5000 different plants. In Europe many of our modern drugs have their origins in traditional medicine.
256
Describe the origins of Morphine.
Morphine has its origins in the use of sap from unripe poppy seed-heads as long ago as Neolithic times. In the 12th century opium from poppies was used as an anaesthetic and, by the 19th century, morphine and opium were being used. These opiate drugs reduce nervous action in the central nervous system. If the nerves cannot carry impulses, then no pain is felt.
