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Biology A Level > Communicable Diseases > Flashcards

Communicable Diseases Flashcards

1
Q

What are phagocytes?

A

Specialised cells in the blood and tissue fluid that engulf and digest pathogens

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2
Q

What are macrophages?

A

Macrophages are larger cells that manufactured in the bone marrow, they play an important role in initiating the specific immune response against a pathogen

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3
Q

What do macrophages do when they engulf a pathogen?

A

They don’t fully digest it, they save the antigen from the surface of the pathogen and move it to a special protein complex on the surface of the cell. The cell becomes a antigen-presenting cell so that other cells of the immune system can recognise the antigen of the pathogen

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4
Q

What are T helper cells?

A

T cells which release interleukins that stimulate B cells to develop and they also stimulate phagocytosis by phagocytes

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5
Q

What are T killer cells?

A

T cells that attack and kill host-body cells that display the foreign antigen

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6
Q

What are T memory cells?

A

T cells which stay in the blood stream even after the pathogen has been destroyed. This provides long term immunity as they can develop into T killer, helper and regulator cells if the pathogen tries to infect the body for a second time

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7
Q

What are T regulator cells?

A

T cells which shut down the immune response after the pathogen has been successfully removed. T helper cells are also involved in preventing autoimmunity

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8
Q

What are plasma cells?

A

B cells that circulate in the blood, manufacturing and releasing antibodies to fight the relevant pathogen

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9
Q

What are B memory cells?

A

B cells that remain in the blood for a number of years and act as the immunological memory, they turn into plasma cells if the pathogen returns

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10
Q

What is health?

A

Being free from illness and disease and having good mental, social and physical well-being

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11
Q

What is a pathogen

A

A microorganism that causes disease

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12
Q

What are the 4 different types of pathogen?

A
  • Bacteria
  • Virus
  • Protists
  • Fungi
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13
Q

What are the main methods of transmission of disease?

A
  • Physical contact, touching a person who is infected
  • Droplet infection, infection is carried in tiny droplets in the air
  • Faecal, drinking water contaminated with the pathogen
  • Transmission by spores which are carried in the air or reside on surfaces or in soil
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14
Q

What is indirect transmission?

A
  • Transmission of a pathogen indirectly via a vector
  • For example, a person with malaria has plasmodium (the parasite for malaria) gametes in their blood
  • If they are bitten by a mosquito, the mosquito sucks their blood and the plasmodium develops into the salivary glands of the mosquito
  • The mosquito then bites an uninfected person and the plasmodium migrates into their liver and then into their blood, they now have malaria
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15
Q

Why are most pathogens only found in warmer climates ?

A

Winter weather reduces pathogens ability to grow and reproduce, they are also damaged and even killed by cold weather

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16
Q

What are a plant’s passive physical defences against pathogens?

A
  • Cellulose cell wall, acts as a physical barrier but also contains many chemical defences that can be activated if a pathogen is detected
  • Lignin thickening of a cell wall, lignin is waterproof and indigestible
  • Waxy cuticles, prevent water collecting on the cell surfaces, the absence of water is a passive defence as pathogens need water to survive
  • Bark, bark contains many chemical defences against pathogens
  • Callose, is a large polysaccharide that is deposited in sieve tubes at the end of growing season, it prevents flow in the sieve tube and therefore can prevent a pathogen spreading around the plant
  • Tylose, tylose is a balloon like-projection that fills the xylem vessel and prevents water flow and therefore spread of pathogens throughout the plant, tylose also contains terpenes which are toxic to pathogens
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17
Q

What are the passive chemical defences that plants have against pathogens?

A
  • Plants contain a variety of anti-pathogenic chemicals such as terpenes, alkaloids, phenols and hydrolytic enzymes
  • Terpenes and tannins are present in tylose and bark respectively before infection, other chemicals are only produced after infection as production of chemicals requires a lot of energy
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18
Q

How does the skin act as a barrier to pathogens?

A
  • The skin acts as a protective layer against pathogens
  • The outer layer of the skin is called the epidermis and consists of cells called keratinocytes
    Cells are produced at the base of the epidermis and then migrate to the surface of the skin, as they migrate they dry out and their cytoplasm is replaced by keratin
  • By the time the cells reach the surface they are dead
  • The keratinised layer of the skin acts as an effective barrier to pathogens
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19
Q

How does blood clotting act as a defence against pathogens?

A
  • The skin is only an effective barrier to pathogens if it is complete
  • If abrasions and lacerations occur the body must prevent excess blood loss by forming a clot, this also provides a temporary seal to prevent infection and repair the skin
  • It is caused by an enzyme cascade
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20
Q

How do mucous membranes act as a defence against pathogens?

A
  • Exchange surfaces are thinner to allow a faster rate of diffusion, this means they are less well protected from pathogens
  • These areas are protected by mucous membranes
  • These membranes contain goblet cells that secrete mucus and underneath the membrane there are extra mucus secreting glands
  • Mucus lines the airways and traps any pathogens that might be in the air
  • Ciliated cells waft the mucus to the top of the trachea where it enters the oesophagus and can then be swallowed
  • It enters the stomach and the acidity of the stomach kills any pathogens trapped in the mucus
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21
Q

How is inflammation a sign of infection?

A
  • Presence of microorganisms is detected by specialised cells called mast cells
  • These release histamines which make capillary walls more permeable to blood plasma and white blood cells
  • This increases the formation of tissue fluid as more white blood cells and blood plasma enter the tissue fluid
  • The excess tissue fluid causes swelling and the excess tissue fluid is drained into the lymphatic system
  • This increases the likelihood of pathogens coming into contact with lymphocytes and a specific immune response being triggered
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22
Q

What are the body’s main primary defences against pathogens?

A
  • The skin
  • Clotting
  • Mucous membranes
  • Histamines
  • Eyes are protected by antibodies and enzymes in the tear fluid
  • Ear canal is lined with wax that traps pathogens
  • Female reproductive system is protected by a mucus plug in the cervix
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23
Q

Why are primary defences non-specific?

A

They prevent entry of any pathogen into the body and not just specific pathogens

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24
Q

What are opsonins?

A

Opsonins are protein molecule that attach to the antigens of a pathogen, this enhances the ability of the phagocytic cells to bind to and engulf the pathogen

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25
Q

What are neutrophils?

A

Neutrophils are a type of white blood cells that are recognisable by their multi-lobed nucleus, they’re manufactured in the bone marrow

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26
Q

How do neutrophils engulf and digest pathogens?

A
  • Neutrophils bind to the opsonins attached to the pathogen
  • The neutrophil then engulfs the pathogen by endocytosis and forms a phagosome
  • Lysosomes fuse with the phagosome and release lytic enzymes which digest the pathogen, this produces harmless waste products that can be absorbed into the cell
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27
Q

What is the function of function of a macrophage?

A
  • Macrophages are manufactured in the bone marrow where they travel in the blood as monocytes to the lymph nodes where they mature into macrophages
  • When a macrophage engulfs a pathogen it doesn’t fully digest it
  • Instead it moves the antigen from the pathogen to a special protein complex on the surface of the cell where the antigen is displayed so that other cells of the immune system can recognise the antigen
  • The special protein complex ensures the antigen presenting cell is not mistaken for a foreign cell and attacked by other phagocytes
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28
Q

What is the role of the antigen presenting cell?

A

The antigen presenting cell moves around the body where it can come into contact with the T and B lymphocytes with the correct recognition site for the antigen. This increases the chance of the antigen coming into contact with these cells and the specific immune response being triggered

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29
Q

What is clonal selection?

A

Activation of the specific B and T cells that have the correct recognition sites for the antigens of the pathogen. There may only be one T and B cell with the correct recognition site for the antigens of the pathogen, this is why the antigen-presenting cell is important as it increases the chances that the correct T and B cells will come into contact with the antigen

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30
Q

What is a pathogen?

A

A microorganism that causes disease

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31
Q

How does a fungal infection occur?

A
  • The mycelium grows under the skin’s surface
  • In plants, the fungus lives in the vascular tissues and the hyphae release extracellular enzymes such as cellulase that digest surrounding tissue
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32
Q

What are hyphae?

A

The branching filaments that make up the mycelium of a fungus

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33
Q

What is the pathogen for TB?

A

Bacteria

34
Q

What is the pathogen for ringrot?

A

Bacteria

35
Q

What is the pathogen for black sigatoka?

A

Fungus

36
Q

What is the pathogen for blight?

A

Protist

37
Q

What is the pathogen for ringworm?

A

Fungus

38
Q

What is the pathogen for malaria?

A

Protist

39
Q

What are the main forms of transmission of pathogens?

A
  • Direct contact, touching someone who is infected or contaminated surfaces
  • Faecal-oral transmission, usually by eating food or drinking water that has been contaminated by the pathogen. The food and water gets contaminated by not having proper sewage systems and also fertilising corps with human sewage
  • Droplet infection, the pathogen is carried in the air in tiny water droplets
  • Spores, which are a resistant stage of the pathogen. These can be carried in the air or reside on surfaces or in soil
40
Q

What social factors can affect transmission of disease?

A
  • Overcrowding
  • Poor ventilation
  • Poor health
  • Homelessness
  • Living or working with people who have migrated from areas where a disease is more common
41
Q

How do plant pathogens infect plants?

A
  • Many pathogens are present in the soil and will infect plant by entering through the roots, this happens more easily if the roots have been damaged by replanting, animals burrowing or storms
  • Many fungi reproduce by producing spores, these spores are carried in the wind and can land on plants
  • Pathogens can enter fruit or seeds and can be distributed when the seeds so that many or all of the offspring are infected
  • Spores or bacteria can become attached to a burrowing insect when it attacks an infected plant, when this beetle attacks another plant, the pathogen is transmitted to that plant, the beetle is acting as a vector. The fungus that causes Dutch elm disease is carried by a beetle.
42
Q

Are pathogens more suited to warm or cool climates?

A

In warm climates pathogens can reproduce and grow more more rapidly and in cooler/winter climates they are damaged and even killed and can’t grow and reproduce. As a result there is a greater variety of diseases found in warmer climates

43
Q

What is callose?

A

A large polysaccharide that blocks phloem sieve tubes as callose deposits in the sieve plate, blocking the perforations which prevents the flow of sap between sieve tube elements

44
Q

What are a plant’s active defences against pathogens?

A
  • Cell walls become thickened and strenghtened with additional cellulose
  • Deposition of callose between the plant cell wall and plasma membrane, this strengthens the cell wall and also blocks the plasmodesmata to block the symplast and vacuolar pathways
  • Oxidative bursts, this is the release of highly reactive oxygen molecules that are capable of damaging the cells of the invading pathogen
  • An increase in production of chemicals
45
Q

What are terpenoids and what is their function?

A

A range of essential oils that have antifungal and antibacterial properties, they may also have a scent, for example menthols and methanones produced by mint plants

46
Q

What are phenols and what is their function?

A

Phenols are organic molecules that have antibiotic and antifungal properties. Tannins, which are a type of phenol found in bark, inhibit insect attack by binding to salivary and digestive enzymes, this deactivates the enzyme. Insects that ingest high amounts of tannins stop growing and eventually die. This helps to prevent the transmission of pathogens

47
Q

What are alkaloids and what is their function?

A

Nitrogen containing compounds that give a bitter taste to herbivores feeding on them. This prevents damage and makes it harder for pathogens to enter the plant. Some alkaloids also inhibit protein synthesis

48
Q

What are defensins and what is their function?

A

Small cysteine-rich proteins that have broad anti-microbial (anti-pathogenic) activity. They cat upon molecules in the plasma membrane of the pathogen, possibly inhibiting ion channels, altering the charge of the cell.

49
Q

What are hydrolytic enzymes and what is their function?

A

Found in the spaces between cells, they include chitinases which break down the chitin in fungal cell walls and lysozymes that break down bacterial cell walls

50
Q

What is necrosis?

A

Deliberate cell suicide, by killing cells surrounding the infection, the pathogen’s access to water and nutrients are restricted and therefore the pathogen will die and not be able to spread further around the plant. Necrosis is brought about by intracellular enzymes that are activated by injury to the plant

51
Q

What is canker in plants?

A

A sunken necrotic lesion in the woody tissue of the plant that causes death of cambium tissue in the bark

52
Q

What proteins stimulate and coordinate the specific immune response?

A

Cytokines

53
Q

How do macrophages attract neutrophils and stimulate B cells to differentiate into plasma cells and release antibodies?

A

Macrophages attract neutrophils by releasing monokines that attract neutrophils by chemotaxis (movement of cells toward a particular chemical), monokines also stimulate the B cells

54
Q

What is clonal expansion and how is it activated?

A

T cells and m,macrophages release interleukins that stimulate clonal expansion (which is the increase in number of T and B cells by mitotic cell division), interleukins also stimulate differentiation of T and B cells

55
Q

What is interferon?

A

A signalling molecule that inhibits virus replication and stimulates the activity of T killer cells

56
Q

Where do T cells mature?

A

In the thymus

57
Q

Where do B cells mature?

A

In the bone marrow

58
Q

What causes an autoimmune disease?

A

T and B cells that are specific to our own antigens are usually destroyed in the early stages of the development of the immune system. An autoimmune disease occurs when our own antibodies attack our own antigens. This could be due to antigens that are not normally exposed becoming exposed to attack

59
Q

How is arthritis caused?

A

Antibodies attacking membranes around the joint causing painful inflammation

60
Q

Describe the structure of an antibody

A
  • Consists of a constant region that is the same in all antibodies, the constant region is where the phagocytes bind when the antibody is acting as an opsonin
  • A hinge region, this is at the centre of the antibody, the hinge region allows flexibility so the antibody can bind to more than one antigen
  • A variable region, this has the specific shape of the antigen
  • Contains many disulfide bridges to hold polypeptide chains together, this means it contains cysteine amino acids
61
Q

Where are the heavy poly peptide chains of an antibody?

A

On the inside of the molecule

62
Q

Where are the light polypeptide chains of an antibody?

A

On the upper outside of the molecule

63
Q

How do antibodies act as opsonins?

A

The antibody binds to the antigen of the pathogen, the antibody then acts as a binding site for neutrophils, so these can bind more easily and destroy the pathogen

64
Q

How do antibodies neutralise pathogens?

A

Some pathogens use antigens as a binding site for attachment to the host cells, if an antibody binds to this then the pathogen can’t attach to host cells meaning that pathogen can’t infect the host cell, it will be phagocytosed as a neutrophil binds to the antibody attached to the antigen of the pathogen

65
Q

What may unspecialised opsonins bind to on a pathogen?

A

The peptidoglycans found in a bacterial cell wall

66
Q

How do antibodies act as agglutinins?

A

As an antibody has two identical binding sites, it is able to cross link pathogens by binding to one pathogen with one binding site and the other pathogen with the other binding site. When many antibodies perform cross linking together, they clump the pathogens together (agglutinate), this clump is non-infective as pathogens are impeded from entering host cells. The clump is also readily engulfed by neutrophils

67
Q

How do antibodies act as anti-toxins?

A

Antibodies bind to toxins released by pathogens, this renders the toxins harmless

68
Q

What is the primary immune response?

A

When an infecting agent is detected the immune system starts to produce antibodies, it takes a few days before the number of antibodies in the blood rises to a level that can combat the infection successfully. This is the primary immune response, once the pathogen has been combatted, the number of antibodies in the blood falls rapidly

69
Q

What is the secondary immune response?

A

If the body becomes infected by the same pathogen again, it won’t have many antibodies left in the blood to fight the infection, however during the first infection, many B memory cells are produced which can quickly differentiate into antibody producing plasma cells as soon as the body recognises that it has been infected by a pathogen with the same antigens. This means that a much higher concentration of antibodies can be produced in a much shorter period of time. This is known as the secondary immune response and is usually quick enough to prevent any symptoms being felt by the host

70
Q

What is a vaccine?

A

Deliberate exposure to antigenic material of a pathogen to stimulate an immune response so that memory cells are produced and immunity to that disease is achieved

71
Q

What are the different types of antigenic material that can be used in vaccination?

A
  • A whole, live microorganisms, but usually ones that are less harmful than those that cause the disease. For example, cowpox was used as a vaccine for smallpox as it was less harmful but had similar enough antigens so that an immune response to cowpox would also provide immunity to smallpox
  • A dead version of the pathogen
  • A harmless or attenuated (weakened) version of the pathogen
  • Preparation of the antigens from the pathogen
  • A toxoid, which is a harmless version of a toxin produced by a pathogen, it has the same antigens as the pathogens
72
Q

What is herd vaccination?

A

Herd vaccination is used to provide immunity to almost all of the population at risk, the disease can no longer spread through the population as everyone will be immune

73
Q

What is ring vaccination?

A

Vaccination of all the people in the immediate vicinity of the disease including the people in the surrounding houses and villages. This prevents spread of disease out of that area

74
Q

How can people catch influenza more than once?

A

The virus readily undergoes mutation in their antigens meaning that the memory cells that the person produced from being infected the first time won’t recognise the new antigen and the person is susceptible to infection again. These mutations of the antigens are known as different strains of disease

75
Q

What is natural active immunity?

A

Immunity provided by memory cells as a result of infection that can rapidly produce antibodies when infected again (eg. immunity to chicken pox after catching it once)

76
Q

What is natural passive immunity?

A

Antibodies provided via the placenta and breast milk, this makes the baby immune to diseases that the mother is also immune to. It is very useful to the baby in the fist year of its life while its immune system is developing

77
Q

What is artificial active immunity?

A

Immunity provided by memory cells produced as a result of vaccination that can rapidly produced antibodies when infected again (eg. immunity to influenza after being injected with a weakened, dead or similar pathogen)

78
Q

What is artificial passive immunity?

A

Immunity provided by injection of antibodies produced by another individual (eg. hepatitis A and B)

79
Q

How does morphine reduce pain?

A

Morphine reduces action potentials in the CNS, if nerves can’t carry action potentials then no pain is felt

80
Q

How could HIV be prevented by using drugs that micic the shape of receptors of T cells?

A

HIV binds to receptors on the T helper cells, if these receptors can be mimicked by a drug then the virus would bind to the receptors of the drug instead, this would block the binding of the virus to the T helper cell receptor

81
Q

How can bacteria become resistant to bacteria?

A

Overuse of antibiotics provides bacteria with selection pressures, because bacteria have a very short lifespan they can mutate quickly. Bacteria that mutate to become resistant to the antibiotic survive and the bacteria that aren’t resistant die out. This means that all bacteria that the antibiotic combats will become resistant a short period of time after the mutation that provides resistance occurs

Biology A Level (21 decks)

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