4.1 Communicable diseases Flashcards
(206 cards)
1
Q
Define pathogen.
A
A microorganism that causes disease.
2
Q
What is the organism in which a pathogen lives called?
A
Host.
3
Q
What are the four types of pathogen?
A
- Bacteria
- Fungi
- Viruses
- Protoctista
4
Q
What kingdom does bacteria belong to?
A
Prokaryotae
5
Q
How is bacteria harmful to their host?
A
Bacteria can reproduce rapidly- in the right conditions, some bacteria can reproduce every 20 minutes.
Once in the host, their presence can cause disease by damaging cells or by releasing waste products and/ or toxins that are toxic to the host.
6
Q
How is fungi harmful to animals?
A
In animals, there are common fungal infections where fungus lives in the skin of the animal, and where its hyphae, which forms mycelium, grow under the skin surface, the fungus can send out reproductive hyphae, which grows to the surface of the skin to release spores. This causes redness and irritation.
7
Q
How is fungus harmful to plants?
A
The fungus often lives in the vascular tissue, where it can gain nutrients. the hyphae release extracellular enzymes, such as cellulases, to digest the surrounding tissue, which causes decay. Leaves will become molted in colour, curl up and shrivel, before dying. Fruit and storage organs (such as tubers) will turn black and decay)
8
Q
What is cellulases and where is it found?
A
Cellulase is an enzyme that digests cellulose. This is an example of on of the extracellular enzymes fungi hyphae release in plants.
9
Q
How are viruses harmful to their host?
A
Viruses invade cells and take over the genetic machinery and other organelles of the cell. They then cause the cell the manufacture more copies of the virus. The host cell eventually bursts, releasing many new viruses which will infect healthy cells.
10
Q
How are protoctista harmful to their host?
A
Protoctista cause damage by entering host cells and feeding of their contents as they grow.
11
Q
What are some examples of a disease caused by bacteria?
A
- Tuberculosis
- Bacterial meningitis
- Ring rot
12
Q
What are some examples of a disease caused by a virus?
A
- HIV/AIDS
- Influenza
- Tobacco mosaic virus
13
Q
What are some examples of a disease caused by a fungus?
A
- Black sigatoka (in bananas)
- Ringworm
- Athletes foot
14
Q
What are some examples of a disease caused by protoctista?
A
- Malaria
- Blight
15
Q
Define direct transmission.
A
Passing a pathogen from host to new host, with no intermediary.
16
Q
Define indirect transmission.
A
Passing a pathogen from host to new host, via a vector.
17
Q
Define vector.
A
An organism that carries a pathogen from one host to another.
18
Q
What are 4 ways a pathogen can be directly transmitted?
A
- Direct physical contact
- Faecal-oral transmission
- Droplet infection
- Transmission by spores
19
Q
How can we reduce direct physic contact spread of pathogens?
A
- Wash hands
- cleaning and disinfecting cuts and abrasions
- Sterilising surgical instruments
- Using condoms
20
Q
How can we reduce faecal-oral transmission spread of pathogens?
A
- Treatment of water and drinking water
- Thorough washing of all fresh food
- Careful preparation and thorough cooking of food
21
Q
How can we reduce droplet infection spread of pathogens?
A
- Catch it - bin it - kill it
- Cover your mouth when sneezing or coughing
- Use a tissue and dispose of it correctly
22
Q
How can we reduce transmission by pores spread of pathogens?
A
- Use of a mask
- Washing skin after contact with soil
23
Q
What social social factors can affect transmission of pathogens?
A
- Overcrowding
- Poor ventilation
- Poor health
- Poor diet
- Homelessness
- living or working with people who has migrated from areas where a disease is more common.
24
Q
What is the plasmodium parasite?
A
Plasmodium parasite causes malaria.
25
How can pathogens infect plants?
* Many **pathogens** are present in the **soil** and will infect the plant by e**ntering the roots-** especially if these have been damaged as a result of replanting, burrowing animals or movement caused by a storm.
* Many f**ungi produce spores** as means of sexual or asexual reproduction. The spores may be carried by the wind- **airborne transmission**- these can enter by the plants stomata.
26
What do pathogens do once it has entered the plant?
* Once inside the plant , it may **infect** all the **vascular tissue**- this allows the pathogen to be distributed throughout the plant. Pathogens infect **leaves**, then, when they shed, they carry the pathogen back to the **soil** where it can **grow and infect** other plants.
* Pathogens can also enter the **fruit** and and **seeds**, and will then be distributed with the seeds- so all the **offspring will be infected**.
27
How can pathogens be indirectly transmitted to plants?
Indirect transmission is often a result of an **insect attack**.
**Spores or bacteria become attached** to a burrowing insect which attacks an **infected plant**. When the insect attacks another plant, the pathogen is **transmitted** to the **uninfected plant**. The insect acts as a **vector**.
28
Why is transmission of pathogens in warmer climates more rapid?
Many protoctista, bacteria and fungi can grow and reproduce quicker in **warm and moist conditions**. As a result, there is a greater variety of diseases to be found in warmer climates, and animals or plants are more likely to be infected.
29
Why is global warming a threat to Europe in terms of pathogens?
Pathogens **reproduce quicker in warm and moist** conditions and in cooler climates, these pathogens may be **damaged or killed by the cold**. This is a threat because as winters get warmer, soon it will **not be cold enough** to kill these pathogens and more pathogens will be around and there will be a greater variety of them.
30
What is callose?
Callose is a large polysaccharide deposit that blocks phloem sieve tubes.
31
What does a plant have instead of an immune system?
* Passive defences
* Active defences
32
Define passive defences. What does this consist of?
These are **defences present before infection**, their role is to prevent entry and spread of the pathogen.
Passive defenses consist of **physical barriers** and **chemicals**.
33
What are some examples of physical defences?
* Cellulose cell wall
* Lignin thickening of cell walls
* Waxy cuticle
* Bark
* Stomata closure
* Callose
* Tylose
34
How does cellulose cell wall act as a physical defence in plants?
This acts as a **physical barrier**. It also contains a variety of **chemical defences** that can be activated when a pathogen is detected.
35
How does lignin thickening of cell walls act as a physical defence in plants?
Lignin is waterproof and almost completely indigestible.
36
How does waxy cuticles act as a physical defence in plants?
These **prevent water collecting** on the cell surfaces. Since pathogens collect in water and need water to survive, the absence of water is a **passive defence.**
37
How does bark act as a physical defence in plants?
Most bark contains a variety of **chemical defences** that work against pathogenetic organisms.
38
How does stomata closure act as a physical defence in plants?
Stomata are possible points for entry for pathogens. Stomata aperture is controlled by guard cells. When pathogens are detected, the **guard cells will close the stomata** in that part of the plant.
39
How does callose act as a physical defence in plants?
Callose is **deposited in the sieve tubes** at the **end of a growing season**. It is deposited around the sieve plates and blocks the flow in the sieve plates and blocks the sieve tube. This can **prevent a pathogen spreading** around the plant.
40
What is a tylose formation?
A tylose is a balloon- like swelling or projection that fills a xylem vessel.
41
How does tylose formation act as a physical defence in plants?
When a tylose is fully formed, it **plugs the xylem vessel** and the vessel can no longer carry water. Blocking the xylem vessels **prevent the spread of pathogens through the heartwood**. The tylose **contains high concentration of chemicals** such as **terpenes** that are toxic to pathogens.
42
How does chemical defences act as a passive defence in plants?
Plant tissues contain a **variety of chemicals** that have **antipathogenic properties**. these include **terpenoids, phenols, alkaloids and hydrolytic enzymes.**
some chemicals such as terpenes in tyloses and tannins in bark, are present before an infection.
43
Why are many antipathogenic chemicals only produces as an active defence?
The production of chemicals **requires a lot of energy**, many chemicals are not produced until the plant detects an infection.
44
How can a plant detect a a pathogen has infected them?
When pathogens attack, **specific chemicals** in their cell walls can be **detected by plant cells**. These chemicals include specific **proteins and glycolipids**.
45
What is active defences in plants?
When a plant has detected a pathogen has invaded, the plant responds by **strengthening the physical defences** and **producing defensive chemicals**.
46
What does active defences include?
* **Cell walls** become **thickened** and **strengthened** with additional **cellulose**.
* **Deposition of callose** between the plant wall and cell membrane near the invading pathogen. It also **strengthens the cell wall** and **blocks plasmodesmata**.
* **Oxidative bursts** the provide highly reactive oxidative molecules capable of damaging the cells of invading pathogens.
* **Increase of production of chemicals**
* **Necrosis**
* **Canker**
47
What is necrosis?
A way a plant does **active defences**.
**Deliberate cell suicide**. A few cells are sacrificed to save the rest of the plant. By killing cells surrounding the infection, the plant can **limit the pathogen's access to water and nutrients** and can therefore **stop it spreading further** around the plant. Necrosis is bought about by **intracellular enzymes that are activated by injury**. These enzymes **destroy damaged cells** and produce brown spots on leaves or dieback.
48
What is a canker?
A sunken neurotic lesion in the woody tissue such as in the main stem or branch. It causes death of the cambium tissue in the bark and is an active defence in plants.
49
What is inflammation?
Swelling and redness of the tissue caused by an infection.
50
What is a mucus membrane?
specialised epithelial tissue that is covered by mucus.
51
What is an organism primary defences?
Defences that prevent pathogens entering the body. These defences are **non-specific,** as they will prevent entry of **any pathogen**.
52
What is the main primary defence?
The skin.
53
How is the skin a primary defence?
The body is covered in skin, preventing the entry of pathogens.
54
What is the outer layer of skin called? What are the cells its made up of called?
The **epidermis**- it consists of layers of cells.
Most of these cells are celled **keratinocytes**.
55
How is the skin made?
**Keratinocytes** are produced by **mitosis** at the **base of the epidermis**. They then **migrate** out to the skin surface. As they migrate, they **dry out** and the **cytoplasm** is **replaced** by the protein **keratin**. This process is called **keratinisation**, it takes about 30 days. By the time the cells reach the surface, they're **no longer alive**. The keratinised layer of dead cells act as an effective barrier to pathogens. Eventually, the dead cells **slough off**.
56
What is the process of the cytoplasm of keratinocytes being replaced by keratin called?
Keratinisation
57
What happens if the skin is damaged?
The body must prevent excess blood loss by forming a **clot**, making a temporary seal to prevent infection, and replacing the skin.
58
What does blood clotting involve?
Calcium ions and at least 12 factors- known as clotting factors. Many of the clotting factors are released from the **platletes** from the damaged tissue. These factors activate an **enzyme cascade**.
59
What happens once the clot has formed to repair the skin?
The clot dries out and forms 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.
60
What happens after a scab has formed?
Firstly **fibrous collagen is deposited** under the scab. Then, **stem cells** in the **epidermis** divide by mitosis to form **new cells**, which **migrate** to the **edges of the cut** and **differentiate** to form **new skin**. **New blood vessels** grow to supply oxygen and nutrients to the new tissues. The **tissues contract** to help draw the edges of the cut together so that a repair can be completed. as the new skin is completed, the **scab will be released**.
61
Why do we need mucous membranes?
Certain substances must enter our blood (e.g.oxygen, nutrients from food) the **exchange surfaces** where this occurs must be **thinner** and are **less protected** from pathogens. The air and food we take in from our environment **may harbour microorganisms,** Therefore, the airways, lungs and digestive system are at risk of infection.
These areas are protected by mucous membranes.
62
What are cilia?
Tiny, hair like organelles that can move.
63
What are primary defences?
* The skin
* Blood clotting and skin repair
* Mucous membrane
* Coughing and sneezing
* Inflammation
* Eyes protected by antibodies and enzymes in tear fluid
* Ear canal is lined with wax, which traps pathogens
* Female reproductive system is protected by a mucus plug in the cervix and by maintaining acidic conditions in the vagina.
64
How is the airways protected by mucous membranes?
Mucous lines the passages and **traps** any **pathogens** that could be in the air. **Cilia move** mucous up to the **top of the trachea**, where it can enter the **oesophagus**. It is **swallowed** and passes down the **digestive system**. Most pathogens in the digestive system are **killed by the acidity** of the stomach (what can have a pH 1-2). This **denatures** the **pathogens enzymes**.
65
What do ciliated epithelial cells do in mucous membranes?
They move in a coordinated fashion to waft the layer of mucous along.
66
Where are mucous membranes found?
* Gut
* Airway
* Genital areas
* Anus
* Ears
* Nose
67
How does coughing and sneezing act as a primary defence?
Areas that are **prone to attack** from pathogens are **sensitive**- this means they **respond to irritation** that may be caused by the presence of **microorganisms** or the **toxins** they may release. These reflexes include **coughing, sneezing and vomiting**. In a cough or sneeze, the sudden **explosion of air** will **carry** with it the microorganisms causing the irritation.
68
What are mast cells?
**Specialised cells** that detect can detect the presence of microorganisms. They release a cell signalling substance called **histamine**.
69
What does histamine do?
Histamine is released by mast cells as a response to the presence of microorganisms.
The main effect of histamine is **vasodilation**, which makes the **capillary walls more permeable to white blood cells** and s**ome proteins**. Blood plasma and phagocytic white blood cells **leave the blood** and **enter the tissue fluid**. This leads to an **increased production of tissue fluid**, which causes **swelling**. Excess tissue fluid is drained into the lymphatic system where **lymphocytes** are stored. This can lead to pathogens coming into contact with the lymphocytes and **initiating specific immune response**.
70
Why is it important blood clots don't form in vessels?
Clots could disrupt blood flow, could cause reduced flow to vital organs, could reduce delivery of oxygen, causing heart attack or stroke.
71
How is thrombin activated by the removal of some amino acids from prothrombin?
A short chain of amino acids could be blocking the active site; removal of this short chain would expose the active site.
72
What is an expulsive reflex?
A sneeze or a cough, which expels air and pathogens quickly.
73
How is inflammation caused?
Dilation of arterioles leading to infected area, increased leakiness of capillaries, more tissue fluid produced.
74
How does smoking lead to increased lung infections?
Cilia are paralysed due ti the tar inhaled and mucus is not removed; pathogens collect in mucus and reproduce.
75
What is the clotting cascade?
A series of enzyme controlled reactions in the blood that leads to the formation of a blood clot.
76
What does the clotting cascade form a blood clot?
Blood **platelets** in a damaged vessel release a chemical called **thromboplastin**, which triggers the **clotting cascade**.
**Thromboplastin** triggers an **enzyme** to catalyse the conversion of the protein **prothrombin** into an enzyme called **thrombin**.
The enzyme **thrombin** catalyses the conversion of soluble **fibrinogen** (found in the blood) into insoluble **fibrin**, forming a **mesh**.
The mesh taps more platelets and red blood cells forming a **blood clot.**
As more platelets are trapped, they restart the process and keep the blood clot forming and growing.
77
What does terpenoids do in plants?
Terpenoids are a type of chemical released as a defence that have **antibacterial and antifungal properties**.
78
What do phenols do in plants?
Phenols are a type of chemical released by plants as a type of defence that have **antibacterial and antifungal properties**. Some of them act as chemical deterrents against herbivores and pathogens.
79
What do alkaloids do in plants? include examples of alkaloids.
Alkaloids give a **bitter taste** to inhibit herbivores from feeding of the plant as a way of defence.
They also act of a variety of **metabolic reactions** via **inhibiting or activating** some enzyme action. e.g. some alkaloids will inhibit protein synthesis.
Examples include nitrogen-containing compounds such as caffeine, nicotine, cocaine, morphine.
80
What do defensive proteins do in plants? What are they?
Defensive proteins are **small cytosine-rich proteins** that was a broad anti-microbial activity.
They act upon molecules in the **plasma membrane** of pathogens, **inhibiting** the action of **ion transporting molecules**.
81
What do hydraulic enzymes do in plans? Give some examples.
Found between cells, they **degrade bacterial walls**.
Examples include chitinases, glucanases and lyzosomes.
82
What is an 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.
83
What is a clonal selection?
Selection of B or T cells that are specific to the antigen.
84
What is cytokines?
Hormone-like molecules used in cell signalling to stimulate the immune response.
85
What is a neutrophil?
A type of **white blood cell** that **engulfs foreign matter** and traps it in large vacuole (phagosome), Which fuses with lysosomes to digest foreign matter.
86
What are opsonins?
**Proteins** that **bind** to the **antigen on a pathogen** and then will **allow pathogens to bind**. They're **not very specific** so can bind to a variety of pathogenic cells.
87
What are antigens?
**Chemical markers** on the outer membrane of an organisms plasma membrane which allows the body to recognise it. They are **proteins or glycoproteins.** They're **specific** to the organism.
88
What is the role of opsonins?
To **enhance** the **ability** of **phagocytic cells** to bind and engulf the pathogen.
89
What is phagocytes?
The **first line of secondary defence** is phagocytosis. Specialised cells in the blood an tissue fluid engulf the pathogen.
90
What are the most common type of phagocytes?
Neutrophils.
91
What is a neutrophil?
The **most common** types of **phagocytes**. They're manufactured in the **bone marrow**. They travel in the blood and often squeeze out of the blood and into the tissue fluid. They're short lived but will be released in large numbers an response to an infection.
92
What do neutrophils do?
They **engulf and digest pathogens**.
They usually die soon after digesting a few pathogens. Dead neutrophils may collect in an area of infection, to form pus.
93
What are the characteristics of a neutrophil?
They have multi-lobed nucleus.
94
What are the stages as a neutrophil engulfs and digests a pathogen?
* Neutrophil **binds to the opsonin** attached to the antigen of the pathogen.
* The **pathogen is engulfed** of endocytosis forming a **phagosome**.
* **Lysosomes fuse** to the phagosome and **release lytic enzymes** into it.
* After digestion, the harmless **products** can be **absorbed** into the cell.
95
How are phagocytes specialised?
They have:
* **receptors** o their plasma membrane that can bind to the opsonin or a specific antigen.
* A **lobed nucleus** that allows that allows the cell to squeeze through narrow gaps.
* A **well developed cytoskeleton** that helps the cell to change shape to engulf the pathogen and to move lysosomes and vacuoles around inside the cell.
* Many **lysosomes** containing lysin.
* Many **mitochondria** to release energy
* A lot of **ribosomes** to synthesis the enzymes involved.
96
What are macrophages? Where are they manufactured?
Macrophages are larger cells manufactured in the bone marrow. They travel in the blood as monocytes before settling in the body tissues- many are found in the lymph nodes where they mature into macrophages.
97
What is the role of macrophages?
Macrophages play an important role in initiating the specific response to invading pathogens.
When a macrophage engulfs a pathogen, it **does not fully digest it**. The **antigen** from the surface of the pathogen is **saved** and moved to a **special protein complex** on the **surface of the cell**. The cell becomes an **antigen-presenting cell**. It **exposes the antigen** on it's surface, so that other cells of the **immune system can recognise the antigen**.
98
Why are macrophages not recognised as pathogens?
The **special protein complex** on the surface of the cell ensures that the antigen-presenting cell is not mistaken for a foreign cell and attacked by other phagocytes.
99
What are the two types of white blood cell?
Phagocytes and lymphocytes.
100
What are the two types of phagocytes?
Neutrophils and macrophages.
101
What are the two types of lymphocytes?
B cells and T cells.
102
What is clonal selection?
**Activation of B and T cells** that brings into play a complex series of events that **lead** to the **production of antibodies** that can **combat** the specific **pathogen** and memory cells that will provide immunity.
103
How is the series of events during an immune response coordinated?
Its coordinates by a number of hormone-like chemicals called **cytokines**.
104
Define antibody?
**Specific proteins** released by **plasma calls** that can **attach** to **pathogenic antigens**.
105
What is a B memory cell?
A cell that **remains in the blood** for a long time, providing **long time immunity.**
106
What is clonal expansion?
An increase in the number of cells by mitotic cell division.
107
What are interleukins?
Signalling molecules that are used to communicate between different white blood cells.
108
Wat are plasma cells?
Derived from the **B lymphocytes**, these are cells that **manufacture antibodies**.
109
What are T helper cells?
Cells that release signalling molecules to stimulate the immune response.
110
What are T killer cells?
Cells that **attack** and destroy our **own body cells** that are **infected** by a pathogen.
111
What are T memory cells?
Cells that remain in the blood for a long time , providing long-term immunity.
112
What are T regulator cells?
Cells that are involved with **inhibiting or ending** the **immune response**.
113
Descirde B and T cells.
B and T cells are **white blood cells** with a **large nucleus** and **specialised receptors** on their **plasma membranes**.
114
What does the immune response produce?
Antibodies
115
What do antibodies do?
neutralise foreign antigens.
116
What does the immune response provide the body?
Provides the body with **immunological memory** through the release of memory cells.
117
What are the 4 types of T cells produced in the immune respone?
* T helper cells
* T killer cells
* T memory cells
* T regulator cells
118
What are the two types of B cells produced in the immune response?
* Plasma cells
* B memory cells
119
What is cell signalling?
The coordinated action of a range of cells because in order to work together effectively, cells need to communicate.
120
How is cell signalling achieved?
through the release of hormone-like chemicals called cytokines.
121
What are some examples of communication using cytokines during the immune response?
* Macrophages release monokines
* T cells and macrophages release interleukins
* Many cells can release interferon
122
What do monokines released by macrophages do?
Some monokines **attract neutrophils** and others **stimulate B cells** to **differentiate** and **release antibodies.**
123
What do interleukins released by macrophages and T cells do?
Stimulates clonal expansion and differentiation of B and T cells.
124
What does the release of interferons from cells do?
Inhibits virus replication and stimulates the activity of killer T cells.
125
What causes an autoimmune disease?
When the immune system attacks part of the body. They usually arise when antibodies start to attack our own antigens- possibly because antigens that are not normally exposed become exposed to attack.
126
What are the 6 stages if the immune response?
* Infection and reproduction of pathogen
* Presentation of antigens
* Clonal selection
* Clonal expansion/ Proliferation
* Differentiation
* Action
127
What are 2 examples of autoimmune diseases?
* **Arthritis**- painful inflammation of a joint. Cause is uncertain however, starts with antibodies attacking he membrane around the joint.
* **Lupus**- causes swelling and pain. It may be associated with antibodies that attack certain proteins in the nucleus in the nucleus and affected tissues.
128
Where are B cells produced and matured?
B cells are produced and matured in the bone marrow.
129
Where are T cells produced and matured?
T cells are produced in the **bone marrow** and and matured in the **thymus gland**.
130
What are the types of antigen presenting cells?
* Macrophages
* Infected cells
* Pathogens in body fluid
131
What is clonal selection?
B and T cells are produces with slightly different receptors on their plasma membrane until a cell is produced with a receptor complimentary to the shape of the specific antigen on the pathogen. After this, clonal expansion takes place.
132
What is clonal expansion?
Clonal expansion, also known as proliferation, takes place after clonal selection because once the correct lymphocyte have been activated, they **increase in number via mitotic cell division**. The body clones it.
133
How are the B cells involved in the immune responce?
When an invading **pathogen** is **detected,** B cells are produced in the **bone marrow**. Each cell is produced with a **slightly different receptor**. The receptor molecules on the plasma membrane of the antigen are proteins that have a shape **complimentary** to the to the shape of the specific antigen. When the correct B cell is found, and it has a complimentary receptor, **clonal expansion** occurs where the B cell is cloned many times so it increases in number. Finally, the clones of B cells **differentiate** into plasma cells and memory cells.
134
How are T cells involved in the immune response?
When antigens are detected from a macrophage, infected cell or pathogen, (**primarily from macrophages**), T cells are produced in the **bone marrow**, then, mature in the **thymus gland** where it receives receptors. Here, **clonal selection** takes place and T cells are produced until a T cell with a complimentary receptor on the cells plasma membrane to the specific antigen the pathogen. Next, **clonal expansion** takes place and the complimentary T cell is cloned by **mitotic cell division**. The T cells differentiate into **4 different types** of cell: T killer cells, T memory cells, T helper cells and T regulator cells.
135
How might T killer cells recognise infected host cells?
Infected host cells may have bits of the pathogen on their surface – these act as antigens.
136
Why are regulator T cells needed?
It would be wasteful to keep producing large numbers of antibodies after the infection has been removed. If the immune system kept producing more and more B and T cells, the blood would soon be filled with these cells, rather than with red blood cells.
137
Why does the immune system not usually attack our own body cells?
B and T cells have receptors that are complementary to specific antigens. Early in development of the immune system, the cells that have **receptors complementary to our own antigens are destroyed**. This means that no B or T cells have receptors that are complementary to our own antigens.
138
Why do cell signalling molecules have a very specific shape?
They have specific target cells or tissue. These target cells possess a cell surface receptor which is complementary in shape to the shape of the cell signalling molecule.
139
What might cause the onset of an autoimmune disease?
If the **antigens** on our own cells and tissues change shape as a result of a **mutation**, they may then **match those of a pathogen**, so that some B and T cells **recognise them as foreign**.
140
What are agglutinins?
**Antibodies** that cause **pathogens** to **stick together**.
141
What are anti-toxins?
**Antibodies** that render **toxins harmless**.
142
What are opsonins?
**Antibodies** that make it **easier** for **phagocytes** to **engulf** the pathogen.
143
What is the primary immune response?
The **initial response** caused by the **first infection**.
144
What is the secondary immune responce?
A more **rapid and vigorous response** caused by a **second** or subsequent **infection** by the **same pathogen**.
145
What is a antigen?
Almost any molecule could act as an antigen, but they are usually **proteins or glycoproteins** in the **plasma membrane** of the **pathogen**.
146
What will the body produce after detecting the presence of a foreign antigen?
Antibodies
147
What are the three main types antibodies?
* Opsonins
* Agglutinins
* Anti-toxins
148
How do opsonins work?
Opsonins bind to the antigens on a pathogen, then act as a binding site for the phagocytic cells, so that these can more easily bind to and destroy the pathogen.
149
How can you describe opsonins?
Opsonins are **antibodies.**
150
What are the two types of antibodies and what do they do?
Some antibodies are **not very specific** and stick to any type of molecule that are not found in the host cell.
Other opsonins are produced as part of the specific immune response and bind to **very specific** antigens.
151
What is neutralisation of a pathogen?
Neutralisation occurs when a **specific opsonin** binds to to a **pathogens antigen**, meaning the pathogen can **no** longer **attach** to a **host cell**.
152
How does agglutinins work?
Because each antibody ha**s two identical binding sites**, it is able to **‘crosslink’ pathogens** by binding on one pathogen with one binding site and then an antigen on another pathogen with it's other binding site. When many antibodies perform this crosslinking they **clump together** (agglutinate) pathogens.
153
What is another way of phasing the antibody that ‘clump together pathogens’?
**Agglutinate** pathogens
154
What are the advantages of agglutinins?
* The agglutinated pathogens are **physically impeded from carrying out some functions**, such as entering host cells.
* The agglutinated pathogens are **readily engulfed by phagocytes**- particularly effective against viruses.
155
How do anti-toxins work?
Some antibodies bind to **molecules** that are released by pathogenic cells. These molecules may be **toxic** and the action of **anti-toxins renders them harmless**.
156
When are antigens produced?
In response to an infection.
157
In the primary immune response to a pathogen, why may the person feel ill?
It may take a **few days** before the **number of antibodies** in the blood **rises** to a level that can **combat** the infection **successfully**.
158
After the primary response, and the infection has been destroyed, what happens to the left over antibodies?
Once the pathogens are dealt with, the number of antibodies in the blood drops rapidly. However, B and T memory cells are left in the blood stream.
159
Why in the secondary response to a pathogen, may the person feel no symptoms?
The secondary response is **much quicker** than the primary response because there are **B and T memory cells** already in the blood stream, meaning, the immune system a]can swing into action more quickly.
160
What is the difference between the primary response and the secondary response?
The secondary response production of **antibodies** **start sooner** and reaches a **higher concertation**.
161
Define active immunity.
Where the **immune system is activates** and manufactures its **own antibodies**.
162
Define artificial immunity.
**Immunity** that is achieved as a result of **medical intervention**.
163
Define epidemic.
A **rapid spread of disease** through a **high proportion of the population**.
164
Define natural immunity.
Immunity achieved through normal life processes.
165
Define passive immunity.
Immunity achieved when antibodies are passed to the individual through breast feeding or an injection.
166
Define vaccination.
A way of stimulating an immune response through **deliberate exposure to antigenic material** so that immunity is achieved.
167
In vaccinations, how does the exposure to antigenic material create immunity?
The immune system treats the antigenic material as a real disease. AS a result, the immune system is activated and manufactures antibodies and memory cells. The memory cells provide the body with long term immunity.
168
What forms of antigenic material is given in vaccinations?
* **Whole living microorganism**- usually ones that are not as harmful as those that cause the real disease- but have very similar antigens.
* **A harmless or weakened version of the pathogenic organism**.
* **A dead pathogen**.
* **A preparation of the antigens from the pathogen**.
* **A toxoid**, Which is a harmless version of a toxin.
169
What is herd vaccination?
Head vaccination 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 spread** through the population and you achieve herd immunity.
In order to be effective, it is essential to vaccinate almost all the population.
170
What is ring vaccination?
Ring vaccination is used when **a new case** of a disease is reported. It involves **vaccinating all the people in the immediate vicinity** of the new cases.
Ring vaccination is also used to prevent diseases spreading in livestock.
171
What is a pandemic?
A world wide epidemic.
172
Why are new strands of pathogens bad?
A new strand would be due to a **mutation** in the pathogens DNA which would cause the **antigen** on it's plasma membrane to **change shape** so the memory cells will have no effect on the original vaccine is likely to no longer be effective.
173
What is an example of natural active immunity.
Immunity provided by antibodies made in the immune system as a result of an infection.
174
What is the example of natural artificial immunity?
Immunity provided by antibodies made in the immune system as a result of vaccination.
175
What is an example of passive natural immunity?
Antibodies provided via the placenta or via the breast milk.
176
What is an example of passive artificial immunity?
Immunity provided by an injection of antibodies made by another individual.
177
Distinguish clearly between an antigen and an antibody.
An antigen is a cell-surface molecule that is specific to the cell; an antibody is an immunoglobulin manufactured by the plasma cells.
178
What is meant by the term immunoglobin?
An immunoglobulin is a **complex protein** associated with the **immune system**. They are found in the blood and are able to bind to antigens.
179
Hoe are plasma cell specialised to their roles?
Plasma cells have a lot of ribosomes, rough endoplasmic reticulum, Golgi apparatus and mitochondria.
180
How does the structure of an antibody enable it to perform its function?
* The **variable region** is specific to the antigen – it has a shape that is complementary to the shape of the antigen.
* The **disulfide bridges** hold the four polypeptide chains together.
* The **hinge region** allows some flexibility so that the molecule can bind to more than one antigen.
* The **constant region** may have a shape that can be recognised by the neutrophils.
181
What is an antibiotic?
A chemical that **prevents the growth of microorganisms**. Antibiotics can be antibacterial or antifungal.
182
What 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 **make new biological systems** that do not exist in nature.
183
Why do we need new medicines to be produced?
* There are **new disease** emerging.
* There are still many diseases for which there are **no** effective **treatments**.
* Some **antibiotic** treatments are becoming **less effective**.
184
Give 7 ways new drugs can be developed.
* Accidental discovery
* Traditional remedies
* Observation of wildlife
* Further plant research
* Research into disease-causing mechanisms
* personalised medicine
* Synthetic biology
185
How can accidental discovery lead to new medicines being discovered?
A scientist makes an observation and sets out trying to explain what he or she has seen. For example, Alexander Fleming accidentally discovered the antibiotic penicillin.
186
How is tritonal remedies a source if new medicines?
Some drugs have been for centuries because people notes that **certain plants or extracts have beneficial effects**. The world health organisation calculates that 80% of the worlds population relies of traditional medicines.
For example: morphine has origins from unripe poppy seed heads.
187
How can observation of wildlife be be source of new medicine?
Many animals **make use of plants with medicinal properties**, for example:
* Monkeys and bears rub citrus oils on their coats as insecticides and antiseptics in order to prevent insect bites and infections.
188
How can further plant research be used as a source of new medicines?
Scientist have used traditional plant medicines and animal behavior as a starting point in their search for new drugs. Research unto the **plants** used for traditional remedies enables scientists to **isolate the active ingredient**- this **molecule** can be **analysed**, and similar molecules can be **manufactured.**
189
How can research into disease-causing mechanisms help find new medicines?
Microorganisms often cause disease by the pathogen **binding to a receptor on the plasma membrane on a cell**. If the receptor **site is blocked**, then the **disease** causing pathogen **cannot gain access to the cell.**
The **glycoprotein receptor** can be **isolated and sequenced**, so that **molecular modeling** can be used to determine the shape of the receptor and can be used to bind to the receptor itself, which would block the virus from entering the cell.
190
How can personalised medicine be used to find new medicines?
It is currently possible to screen genomes of plats or microorganisms to identify potential medicinal compounds from the DNA sequences. However, it is hoped in the future that this technology can advance and make it possible to **sequence the genes** from **individuals** with particular **conditions** and **develop specific drugs**- this is personalised medicine.
191
How can synthetic biology be used to make new medicines?
Synthetic biology consists of **developing new molecules**- in particular enzymes that mimic biological systems.
192
Why have antibiotics become less effective.
Through the over-use and misuse of antibiotics of antibiotics, it has enabled microorganisms to develop resistance.
193
Give 2 named examples of bacteria that has become resistant to may antibiotics?
* C. diff (Clostridium difficile)
* MRSA (methicillium-resistant Staphylococcus aureus)
194
Why is it important to have a reporting procedure of new diseases in order to use vaccines effectively?
Primary healthcare may not be well developed, people may live a long way from a health center, people may not be educated to recognise certain diseases – but **doctors need to know** that the **disease has occurred** and its **spread**, in order to use vaccines effectively.
195
Why is using live organisms in vaccines provide better immunity compared to using dead pathogens or preparations of the antigen?
Live organisms **reproduce and increase in numbers** just like a pathogen would; this **stimulates the immune system** to create a **full response**.
196
How does herd vaccination protect us from diseases?
If everyone (or the majority) is vaccinated, then the pathogen cannot reproduce inside most hosts. Even if it infects an unvaccinated person, it is unlikely to be transmitted to another host.
197
Why does passive immunity only provide short term immunity?
Passive immunity is provided by an external supply of antibodies – these are proteins and will not last long in the body. They may even act as antigens and be attacked by antibodies from our immune system. No memory cells will be made.
198
What diseases or conditions may make a person ‘at risk’ from influenza?
Age, chronic heart disease, asthma, being HIV positive, diabetes.
199
What is the difference between herd vaccination and ring vaccination?
Herd vaccination is where everyone, or almost everyone, is vaccinated. Ring vaccination is vaccinating people around the site of the outbreak, so that the pathogen will not be transmitted across that ring to the whole population.
200
What is Influenza?
Influenza (also known as flu) is a killer disease caused by a virus.
201
How may have our ancestors have discovered that sap from unripe poppy seed-heads could act as an anesthetic?
Someone who has been hurt may have been given unripe poppy seeds to eat, and noticed an effect on the level of pain.
202
Describe how a drug that binds to antigens of a pathogen can prevent transmission.
If the drug binds to the receptor that is used to bind to the host cell, then the virus cannot bind to the host cell – transmission has effectively been prevented.
203
What is the link between the base sequence in the gene and the shape of a protein molecule such as a receptor or an enzyme?
The base sequence carries the code for the sequence of amino acids in the protein; the shape of the protein depends upon the base sequence.
204
How can a drug inhibit the action of an enzyme?
The drug could be a similar shape to the substrate and fit into the active site of the enzyme. Alternatively, it could fit another part of the enzyme (an allosteric site) and affect the shape of the active site indirectly.
205
Why is it important to use antibiotics correctly?
If antibiotics are not used properly, some bacteria may survive the treatment.
206
How may a microorganism become resistant to an antibiotic?
Bacteria that survive a treatment will be slightly resistant to the antibiotic and the antibiotic acts as a selective force which selects the resistant individuals. When they reproduce, some of their offspring may be more resistant, thus resistance evolves.
