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AS OCR Biology > Unit 4.1- Communicable diseases > Flashcards

Unit 4.1- Communicable diseases Flashcards

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1
Q

Examples of diseases caused by bacteria:

A
  • TB
  • Bacterial meningitis
  • Ring rot (plants)
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2
Q

Examples of diseases caused by viruses:

A
  • HIV/AIDS
  • Influenza
  • Tobacco mosaic virus (plants)
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3
Q

Examples of diseases caused by fungi:

A
  • Black sigatoka (bananas)
  • Ringworm (cattle)
  • Athlete’s foot
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4
Q

Examples of diseases caused by protacista:

A
  • Blight (tomatoes and potatoes)

- Malaria

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5
Q

Vector definition:

A

An organism that carries a pathogen from one host to another

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6
Q

What is the life cycle of a pathogen?

A
  • Travel from one host to another (transmission)
  • Entering the host’s tissues
  • Reproducing
  • Leaving the host’s tissues
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7
Q

Examples of plants’ physical defences against pathogens:

A
  • Cellulose cell wall
  • Lignin thickening of cell walls
  • Waxy cuticles
  • Bark
  • Stomatal closure
  • Callose
  • Tylose
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8
Q

How is a cellulose cell wall a plant’s defence against pathogens?

A

Physical barrier and contains a variety of chemical defences that can be activated when a pathogen is detected

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9
Q

How is lignin thickening of cell walls a plant’s defence against pathogens?

A

Waterproof and almost completely indigestable

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10
Q

How are waxy cuticles a plant’s defence against pathogens?

A

Prevent water collecting on the cell surfaces. Pathogens collect in water and need it to survive

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11
Q

How is bark a plant’s defence against pathogens?

A

Contains chemical defences

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12
Q

How is stomatal closure a plant’s defence against pathogens?

A

Stomata are possible points of entry for pathogens. Guard cells will close the stomata of pathogens are detected

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13
Q

How is callose a plant’s defence against pathogens?

A

Callose is a large polysaccharide deposit that blocks old phloem sieve tubes. This can prevent pathogens from spreading around the plant

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14
Q

How is tylose formation a plant’s 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 so it can’t transport water. This prevents the spread of pathogens. The tylose also contains a high concentration of chemicals that are toxic to pathogens

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15
Q

Examples of plants’ chemical defences against pathogens:

A
  • Terpenoids
  • Phenols
  • Alkaloids
  • Hydrolytic enzymes
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16
Q

Why are many chemicals not produced until after the plant detects infection?

A

The production of chemicals requires a lot of energy

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17
Q

Examples of active defences in plants:

A
  • Cell walls becoming thicker and strengthened with additional cellulose
  • Deposition of callose between the plant cell wall and cell membrane near the invading pathogen
  • Oxidative bursts that produce highly reactive oxygen molecules capable of damaging the cells of invading pathogens
  • An increase in the production of chemicals
  • Necrosis
  • Canker
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18
Q

How is the chemical Terpenoids an active defence for plants against infection?

A

Have a range of essential oils that have antibacterial and antifungal properties. They may also create scent.

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19
Q

How is the chemical Phenols an active defence for plants against infection?

A

Have antibacterial and antifungal properties.

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20
Q

How are tannins an active defence for plants against infection?

A

Found in bark and inhibit attack by insects. They bind to salivary proteins, deactivating the enzymes. Insects that ingest high amounts of tannins do not grow and will eventually die

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21
Q

How are alkaloids an active defence for plants against infection?

A

They give a bitter taste to prevent herbivores feeding. Some inhibit protein synthesis, this prevents grazing by larger animals, so reduces damage

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22
Q

How are defensive proteins (defensins) an active defence for plants against infection?

A

These are small cysteine-rich proteins that have broad anti-microbial activity. They act on molecules in the plasma membrane of pathogens, possibly inhibiting the action of ion transport channels.

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23
Q

How are hydrolytic enzymes an active defence for plants against infection?

A

Found in the spaces between cells. They include:

  • Chitinases: break down the chitin found in fungal cell walls
  • Glucanases: hydrolyse the glycosidic bonds in glucans
  • Lysozymes: capable of degrading bacterial cell walls
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24
Q

Necrosis definition:

A

Deliberate cell suicide. By killing cells surrounding infection, the plant can limit the pathogen’s access to water and nutrients.

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25
What is necrosis brought about by?
Intracellular enzymes that are activated by injury. The enzymes destroy damaged cells and produce black spots on leaves.
26
Canker definition:
A sunken necrotic lesion in the woody tissue such as the main stem or branch. It causes death of the cambium tissue in the bark
27
Inflammation definition:
Swelling and redness of tissue caused by infection
28
Mucous membrane definition:
Specialised epithelial tissue that is covered by mucous
29
Primary defences definition:
Those that prevent pathogens entering the body
30
Are primary defences specific?
No, they prevent entry of any type of pathogen
31
What is the main primary defence?
The skin
32
How does the skin as as a defense against pathogens?
Keratinocytes are produced my mitosis at the base of the epidermis. They then migrate out to the surface of the skin. As they migrate, they dry out and their cytoplasm is replaced by keratin. This process is called keratinisation and takes about 30 days. By the time the cells have reached the surface they are no longer alive and they act as an effective barrier to pathogens. Eventually the dead cells slough off
33
How does a scab work?
It shrinks as it dries, drawing the sides of the cut together. This makes a temporary seal, underwhich the skin is repaired
34
How is skin repaired under a scab?
- There is deposition of fibrous collagen under the skin - 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 - New blood vessels grow to supply oxygen and nutrients to the new tissues - The tissues contract to help draw the edges of a cut together so that repair can be completed - As the new skin is completed the scab will be released
35
Why are the airways, lungs and digestive system at risk of infection?
The exchange surfaces are thinner and less well protected from pathogens
36
What are the airways, lungs and digestive system protected from pathogens by?
Mucous membranes
37
What do mucous membranes consist of?
The epithelial layer contains goblet cells. There are also extra mucous secreting glands under the epithelium
38
How do mucous membranes work in the airways?
- The mucous lines the passages and traps any pathogens - The epithelium also has ciliated cells which move in a coordinated fashion to waft the layer of mucus along - They love the mucous up to the top of the tray heart where it can be swallowed down the oesophagus - Most pathogens can then be killed in the acidic stomach (PH 1-2) this denatures the pathogens' enzymes
39
Where are mucous membranes found?
- Airways - Gut - Genital areas - Anus - Ears - Nose
40
What do mast cells do?
Detect the presence of microorganisms in the tissue. They then release a cell signalling substance called histamine
41
What does histamine do?
- Helps to combat infection. - Causes vasodilation and make the capillary walls more permeable to WBCs and some proteins. - Blood plasma and phagocytic WBCs leave the blood and enter the tissue fluid. - This causes 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 the pathogens coming into contact with the lymphocytes and initiating the immune response
42
How are our eyes protected against pathogens?
- Eyebrows - Eyelashes - Antibodies and enzymes in the tear fluid
43
How is the female reproductive system protected against pathogens?
- There is a mucus plug in the cervix | - Relatively acidic conditions
44
Opsonins definition:
Proteins that bind to the antigen on a pathogen and then allow phagocytes to bind
45
When are secondary defences against pathogens used?
When they have already entered our body
46
What are antigens made of?
Proteins or glycoproteins
47
What do opsonins do?
Attach to the antigen on the surface of the pathogen. Some are not very specific so can attach to a variety or pathogens. They make it easier for phagocytes to bind to and engulf the pathogen
48
What are the different types of phagocytes?
- Neutrophils | - Macrophages
49
What are the features of neutrophils?
- Multi-lobed nucleus - Manufactured in bone marrow - Squeeze out of the blood into the tissue fluid - Short lived but will be released in large numbers as a result of infection - Contain a large number of lysosomes which engulf and digest pathogens - Usually die soon after engulfing a few pathogens - Dead neutrophils form in an area of infection to form pus
50
How does phagocytosis work?
- Neutrophil binds to the opsonin attached to the antigen on the pathogen - The pathogen is engulfed by endocytosis forming a phagosome - Lysosomes fuse to the phagosome and release lytic enzymes into it - After digestion, the harmful products can be absorbed into the cell
51
Features of macrophages:
- Larger that neutrophils - Travel in the blood as monocytes - Many are found in the lymph nodes where they mature into macrophages
52
Dendratic cells definition:
Type of macrophage. Found in more peripheral tissues
53
What do macrophages do?
When it 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 and presents the antigen on the surface so that other cells in the immune system can recognise the antigen
54
What does the special protein complex on an antigen presenting cell do?
Ensures the antigen presenting cell is not mistaken for a foreign cell and attacked
55
What is antigen presentation?
Once the macrophage becomes an antigen-presenting cell, it increases the chance of the antigen coming into contact with the B and T lymphocytes
56
What is the specific immune response?
The activation of B and T cells is called clonal selection, which results in the production of antibodies that provide long term immunity
57
Antibodies definition:
Specific proteins released by plasma cells that can attach to pathogenic antigens
58
Antigen presenting cell definition:
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
59
Clonal selection definition:
Selection of a specific B or T cell that is specific to the antigen
60
B memory cells definition:
Cells that remain in the blood for a long time, providing long term immunity
61
Clonal expansion definition:
An increase in the number of cells by mitotic cell division
62
Interleukins definition:
Signalling molecules that are used to communicate between different WBCs
63
Cytokines definition:
Hormone-like molecules used in cell signalling to stimulate the immune response
64
Neutrophil definition:
A type of white blood cell that engulfs foreign matter an traps it in a large vacuole (phagosome) which fuses with lysosomes to digest the foreign matter
65
Plasma cell definition:
Derived from the B lymphocytes, these are the cells that manufacture antibodies
66
T-helper cells definition:
Cells that release signalling molecules to stimulate the immune response
67
T-killer cells definition:
Cells that attack and destroy our own body cells that are infected by pathogens
68
T-memory cells definition:
Cells that remain in the blood for a long time, providing long term immunity
69
T-regulator cells definition:
Cells that are involved with inhibiting or ending the immune response
70
What types of cells do B lymphocyes differentiate into?
- Plasma cells | - B-memory cells
71
What types of cells do T lymphocyes differentiate into?
- T-helper cells - T-killer cells - T-memory cells - T-regulator cells
72
Examples of autoimmune diseases:
- Arthritis | - Lupus
73
What are the symptoms of arthritis?
Painful inflammation of a joint. Starts with antibodies attacking membranes around a joint
74
What are the symptoms of lupus?
Can affect any part of the body, causing swelling and pain. Antibodies attack certain proteins in the nucleus in cells of affected tissues
75
Why are there (usually) not any B or T cells specific to our own antigens?
They are destroyed during early development of the immune system
76
Agglutinins definition:
Antibodies that cause pathogens to stick together
77
Anti-toxins definition:
Antibodies that render toxins harmless
78
Primary immune response definition:
The initial response caused by first infection
79
Secondary immune response definition:
A more rapid and vigorous response caused by a second or subsequent infection by the same pathogen
80
What are antigens usually made of?
Proteins or glycoproteins in the plasma membrane of a pathogen
81
What are antibodies made of?
Immunoglobulins- complex proteins produced by the plasma cells in the immune system
82
What is the structure of an antibody like?
- Light polypeptide chain in the top bit - Heavy polypeptide chain in the bottom bit - Disulfide bridges to hold polypeptide chains together - Hinge region to allow flexibility so they can grip more than one antigen at once - Flower bits at top are the variable region, specific to a certain antigen - The rest is the constant region which is the same in all antibodies. It may have a site for the easy binding of phagocytic cells
83
Active immunity definition:
Where the immune system is activated and manufactures its own antibodies
84
Artificial immunity definition:
Immunity that is achieved as a result of medical intervention
85
Epidemic definition:
A rapid spread of a disease through a large proportion of the population
86
Natural immunity definition:
Immunity achieved through natural life processes (includes vaccines because body naturally produces antbodies)
87
Passive immunity definition:
Immunity achieved when antibodies are passed to the individual through breast feeding or injection
88
Vaccination definition:
A way of stimulating an immune response so that immunity is achieved
89
What forms can the pathogenic material in vaccines take?
- Whole, live organisms - A harmless or weakened version of the pathogen - A dead pathogen - A preparation of the antigens from a pathogen - A toxoid (harmless version of a toxin)
90
What are herd vaccinations?
When about 80% of a population is vaccinated the disease can no longer spread
91
What are ring vaccinations?
Used when a new case of a disease is reported. It vaccinates the people in the immediate vicinity of the new case(s). Also used in many parts of the world to prevent the spread of livestock disease
92
What are unstable pathogens?
Pathogens which regularly undergo mutations which change their antigens, such as influenza, meaning it can be transmitted to people who were immune
93
Who is particularly at risk from influenza?
Those aged over 65 or with respiratory tract problems. Vaccinations are available for these people. The strains of flu in the immunisation programme are changed every year

AS OCR Biology (12 decks)

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