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Biology Module 4 > 4.1 DIsease and the Immune System > Flashcards

4.1 DIsease and the Immune System Flashcards

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1
Q

what is a pathogen

A

an organism that causes disease

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2
Q

what is disease

A

a condition that impairs the normal functioning of an organism

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3
Q

what are the 4 types of pathogen

A

bacteria, virus, fungus and protoctista

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4
Q

outline bacteria as a pathogen

A
  • prokaryotic organisms
  • only some are pathogenic
  • can be classed by:
    1) their basic shapes
    2) their cell walls (Gram positive will turn purple blue once stained, and Gram negative will appear red
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5
Q

outline viruses as a pathogen

A
  • non-living
  • genetic material surrounded by protein
  • bacteriophages are viruses which attack bacteria, by taking over the cells biochemistry and using them to replicate and make more viruses
  • all pathogenic
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6
Q

outline protoctista (protista) as a pathogen

A
  • single-celled eukaryotic organisms and cells grouped into colonies
  • small amount are pathogens
  • parasitic (use people and animals as their host organism)
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7
Q

outline fungus as a pathogen

A
  • not too bad in animals, but cause devastation in plants
  • eukaryotic organisms, often multicellular, can be single
  • can be saprophytes (feed on dead or decaying matter)
  • or parasites (feed on living matter, and are pathogenic)
  • produce loads of tiny spores when reproducing, so can spread rapidly
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8
Q

what are the 2 modes of action of pathogens

A

damaging host tissue directly:
- viruses, which take over cell metabolism, by inserting viral genetic DNA into host cell, reproducing more viruses and bursting the cell
- protoctista, which enter cells and break them as they reproduce
- fungus, which digest and destroy living cells
producing toxins which which damage host tissue:
- bacteria, which produce toxins which poison or damage the host cells
- fungi can also do this

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9
Q

what are the 3 bacterium diseases

A
  • Tuberculosis:
    affects animals, particularly humans and cattle (destroying lung tissue and suppressing the immune system)
  • Bacterial Meningitis:
    affects humans
  • Ring Rot:
  • affects plants, such as potatoes and tomatoes
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9
Q

what is a communicable disease

A

disease that can spread between organisms via use of pathogens

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10
Q

what are the 3 viral diseases

A
  • HIV/AIDS:
    affects humans, and begins with HIV, which destroys the immune system, so you’re more likely to get other infections too, called a retrovirus
  • Influenza:
    affects animals, including humans, which leaves the airways open to secondary infection through destroying ciliated epithelial cells, mutate regularly
  • Tobacco Mosaic Virus:
    affects plants, mainly tobacco and tomato
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11
Q

what are the 3 fungal infections

A
  • Black Sigatoka:
    affects banana plants, turning the leaves black
  • Ringworm:
    affects cattle and other mammals, creams enough to cure the crusty, itchy patches
  • Athlete’s foot:
    affects humans, a form of ringworm
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12
Q

what are the 2 protoctista diseases

A
  • Potato/Tomato Late Blight:
    affects potatoes and tomatoes
  • Malaria:
    affects animals, including humans, spread by mosquitoes as a vector, with female mosquitoes taking 2 blood meals for protein when laying eggs, passing on the virus (easily prevented by removing standing water where they breed, insecticides, nets, window and door screens, and long sleeved clothing)
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13
Q

what are the two ways that communicable diseases can spread

A
  • direct transmission: disease is transmitted directly from one organisms to another
  • indirect transmission: when a disease is transmitted from one organism to another via an intermediate
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14
Q

explain how direct transmission can occur

A
  • droplet infection (coughing or sneezing tiny droplets of mucus or saliva directly onto someone)
  • sexual intercourse, kissing or contact of bodily fluids
  • direct skin to skin contact through touching
  • inoculation (through a break in the skin), such as sharing needles or bites
  • ingestion of contaminated food or drink
  • faeces on hand
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15
Q

give examples of direct transmission at play

A
  • HIV transmitted directly between humans via sexual intercourse
  • Athlete’s foot spread via touch
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16
Q

explain how an indirect transmission can occur

A
  • fomites (inanimate objects like bedding or socks)
  • airborne/droplet infections, when minute droplets of saliva and mucus stay in the air, and are later inhaled
  • vectors (another organism/host), or water
  • food
17
Q

examples of indirect transmission at play

A
  • potato/tomato late blight: spread when spores are carried between plants, first in air and then water
  • malaria: spread via mosquitoes, which are vectors as they dont cause the disease themselves, but just spread it between organisms
18
Q

what are factors which affect disease transmission

A
  • overcrowded living conditions
  • climate
  • social factors
  • poor nutrition and compromised immune system
19
Q

example of overcrowding increasing the spread of communicable disease

A

TB:
- spread directly via droplet infection and indirectly ad bacteria can remain in air for long periods of time, and infect new people
- infection increases when loads of people live crowded together in a small space

20
Q

examples of climate increasing the spread of communicable diseases

A
  • potato/tomato late blight, which is especially common in wet summers, as spores need water to spread
  • malaria, which is most common in tropical countries, which are humid and hot, the ideal conditions for mosquitoes to breed
21
Q

examples of social factors increasing the transmission of communicable diseases

A

HIV:
- limited access to good healthcare means people are less likely to be diagnosed and treated for HIV, and the most effective anti-HIV drugs are less likely to be available, so virus is more likely to be spread
- limited health education, to inform people about how HIV is transmitted and how it can be avoided, e.g. through safe-sex practises like using condoms

22
Q

direct transmission of communicable diseases in plants

A

direct contact of a healthy plant with any part of a diseased plant

23
Q

indirect transmission of communicable diseases in plants

A
  • soil contamination: infected plants can leave pathogens and spores in the soil, which can infect the next crop (also with compost, if can survive the composting cycle)
  • vectors: wind, water (swimming through the surface film of water on leaves), animals (e.g. insects and birds as they feed) and humans (hands, clothing, fomites and during transportation)
24
Q

what affects the transmission of communicable diseases in plants

A
  • varieties of crops susceptible to disease
  • overcrowding, increasing the likelihood of contact
  • poor mineral nutrition reducing resistance
  • damp, warm conditions
  • climate change (increases rainfall and wind, vectors moving to different area)
25
Q

what are the physical defences plants have against pathogens

A
  • leaves and stems have a WAXY CUTICLE, providing a physical barrier against pathogen entering, and may stop water from collecting on leaf, reducing risk of infection by pathogens transferred between plants in water
  • plant cells themselves are surrounded by a CELL WALL, forming a physical barrier to any pathogens that make it past the waxy cuticle
  • plants produce a polysaccharide called CALLOSE: gets deposited between cell walls and plasma membranes during times of stress (pathogen invasion). the depositions make it harder for pathogens to enter the cell. depositions at the plasmodesmata (small channels in the cell wall) may limit spread of viruses between cells
26
Q

what are the plant chemical defences against pathogens

A
  • produce ANTIMICROBIAL CHEMICALS, including antibiotics which kill pathogens and inhibit their growth
  • e.g. producing saponins, thought to destroy the cell membranes of fungi and other pathogens
  • e.g. producing phytoalexins, which inhibit the growth of fungi and other pathogens
  • also secrete chemicals which are TOXIC TO CHEMICALS, which reduce the amount of insect-feeding in plants, and therefore reduce the risk of infections by plant viruses carried by insect vectors
27
Q

what do primary, non-specific defences do

A

prevent pathogens from entering an organisms and causing disease

28
Q

what does non-specific mean when talking about animal defences

A

defences that work in the same way for all pathogens

29
Q

how does the skin work as a barrier to prevent infection

A
  • acts as a physical barrier, blocking pathogens from entering the body
  • acts as a chemical barrier, producing chemicals (sebum) that are antimicrobial and can lower pH, inhibiting the growth of pathogens
30
Q

how does the mucus membrane act as a barrier to prevent infection

A
  • protect the body openings that are exposed to the environment (mouth, nostrils, ears, genitals and anus)
  • some membranes secrete mucus, a sticky substance that traps pathogens and contains antimicrobial enzymes (lysozymes)
31
Q

how does blood clotting act as a barrier to prevent infection

A
  • a blood clot is a mesh of protein (fibrin) fibres
  • blood clot plug wounds to prevent pathogen entry and blood loss
  • formed by a series of reactions/cascade of events that take place when platelets (fragments of cells in the blood) are exposed to damaged blood vessels, releasing substances that form the fibrin
32
Q

how does inflammation act as a barrier to prevent infection

A
  • swelling, pain, heat and redness
  • triggered by tissue damage,
  • mast cells in damaged tissues are activated, and release molecules
  • release histamines, which increase the permeability of the blood vessels, so they start to leak fluid into the surrounding areas (now tissue fluid)
  • this causes swelling (and pain) and helps to isolate any pathogens that may have entered the damaged tissue
  • histamines also cause vasodilation, widening of the blood vessels, which increases blood flow to the affected area
  • increases temperature and stops pathogens from reproducing
  • cytokines also present, which attract white blood cells to the area to fight off any pathogens that may be present
33
Q

explain how wound repair acts as a barrier to prevent infection

A
  • skin is able to repair itself in an event of an injury, and reforms a barrier against pathogen entry
  • surface is repaired by an outer layer of skin cells dividing and migrating to the edges of the wound
  • the tissue below the wound then contracts to bring the edges of the wound close together
  • it is repaired using collagen fibres, too many fibres and you’ll end up with a scar
34
Q

how do expulsive reflexes act as a barrier to prevent infection

A
  • coughing and sneezing
  • sneeze: when mucus membranes in the nostrils are irritated by things such as dust and dirt
  • cough: stems from an irritation in the respiratory tract
  • both are an attempt to expel foreign objects, including pathogens from the body
  • happen automatically
  • vomiting and diarrhea too
35
Q

what are phagocytes

A

specialised white blood cells that engulf and destroy pathogens

  • 2 types: neutrophils and macrophages, present in blood and tissue
36
Q

what is pus

A

dead neutrophils and pathogens

37
Q

what are the first few steps of phagocytosis

A

1) pathogen produces chemicals that attract phagocytes
2) phagocytes recognize the non-human proteins on the pathogen (still a non-specific response, as just recognises all as non-self cells and pathogens)
3) phagocyte engulfs the pathogen and encloses it in a vacuole called a phagosome (form of vesicle)
4) phagosome combines with lysosomes in the WBC and forms a phagolysosome
5) enzymes from the lysosome digest and destroy the pathogen

38
Q

what are the additional steps of phagocytosis for macrophages

A
  • once the pathogen has been digested:
    1) the WBC combines antigens from the pathogens surface membrane with major histocompatibility complex (MHC)
    2) the MHC moves the pathogens antigens to the macrophages own surface membrane
    3) becomes an antigen-presenting cell (APC)
    4) antigen now stimulates other cells involved in the specific immune system response, alerting other WBC to area
39
Q

how do cytokines assist in phagocytosis

A
  • released by phagocytes that have engulfed the pathogen
  • cell-signalling molecules that inform other phagocytes that the body is under attack
  • stimulates the WBCs to move towards the area of attack
  • also increase the body temperature
  • and stimulate the specific immune system
40
Q

what is the role of opsonins in the process of phagocytosis

A
  • chemicals that bind to pathogens and “tag” them so that they are more easily recognised by phagocytes
  • most phagocytes have receptors on their cell membranes that bind to common opsonins, and the phagocyte can then engulf the pathogen

Biology Module 4 (3 decks)

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