chapter 12 communicable diseases Flashcards
(88 cards)
1
Q
what are the 4 types of pathogen?
A
bacteria, fungi, viruses and protoctista
2
Q
what is a pathogen?
A
microorganisms that cause disease
3
Q
what is a vector?
A
living or non living factor that transmits a pathogen from one organism to another e.g mosquito for malaria and water for cholera
4
Q
what are the two main ways bacteria can be classified?
A
•their basic shapes (spherical is cocci, rod shaped is bacilli)
•by their cell wall structure (gram positive and negative bacteria)
5
Q
what is gram positive bacteria?
A
bacteria with cell walls that stain purple-blue with gram stain e.g. MRSA
6
Q
what is gram negative bacteria?
A
bacteria with cell walls that stain red with gram stain e.g. E.Coli
7
Q
what is the average size of viruses?
A
0.02-0.03micrometres (~50x smaller than bacteria)
8
Q
what is the basic structure of a virus?
A
some genetic material (DNA or RNA) surrounded by a protein
9
Q
how do bacteria reproduce?
A
binary fission
10
Q
how do bacteria damage cells?
A
produce toxins
11
Q
how do viruses attack cells?
A
invade cells taking over genetic material causing cell to produce more viruses eventually bursting
12
Q
how do protists attack cells?
A
entering host cell and feeding on contents
13
Q
how do fungi reproduce?
A
they release spores
14
Q
describe how viruses damage host cells directly.
A
•they attach to host cell
•they insert the viral nucleic acid
•the cell replicates the viral nucleic acid
•the cell synthesises viral proteins
•viruses are assembled
•lysis of host cell
15
Q
how do fungi attack cells?
A
digest living cells and some produce toxins
16
Q
what are some ways bacterial toxins attack host cells?
A
break down cell membranes, damage or inactivate enzymes, interfering with cell genetic material so they cannot divide
17
Q
what is hyphae and mycelium?
A
hyphae are thread like filaments making up the body of the fungi, mycelium is a network of these hyphae.
18
Q
what is ring rot?
A
a gram positive bacterial plant disease that damages leaves, tubers and fruit. it has no cure
19
Q
what is tobacco mosaic virus (TMV)?
A
•virus that infects plants. it damages leaves, flowers and fruit meaning they can’t photosynthesise, stunting growth and reducing yields.
20
Q
what is potato blight?
A
fungal like protist plant disease. hyphae penetrate host cells, destroying leaves and fruit.
21
Q
what is black sigatoka?
A
fungal plant disease affecting bananas which attacks and destroys the leaves. hyphae penetrate and digest cells turning the leaves black
22
Q
what is tuberculosis?
A
bacterial animal disease damaging lung tissue and suppressing immune system. cured by antibiotics and prevented by vaccination
23
Q
what is bacterial meningitis?
A
bacterial animal disease that affects the meninges of the brain which can spread to the rest of the body causing sepsis/ rapid death. antibiotics will cure disease if given early and vaccines protect against some forms
24
Q
what is HIV/AIDS?
A
a viral animal infection targeting t-helper cells. it gradually destroys the immune system so affected people are more susceptible to other diseases. HIV is a retrovirus with RNA as its genetic material. it has no cure or vaccine but anti retrovirals slow progress of disease
25
what is influenza?
viral animal infection of cilliated epithelial cells in gas exchange system. it kills them leaving airways open to secondary infections. no cure but vulnerable people have flu vaccines each year to combat fast mutating virus
26
what is malaria?
protist animal disease spread by infected mosquitoes (vector). they reproduce inside female mosquitoes which take blood meals to gain protein before laying eggs. plasmodium is transmitted when she feeds. it invades erythrocytes, the liver and brain. no vaccine and limited cures but controlling the vector reduces transmission. (insecticides and mosquito nets)
27
what is ring worm?
a fungal animal disease causing grey-white crusty infectious circular areas of skin. may be itchy but anti fungal creams are a good cure
28
what is athletes foot?
a fungal human disease caused by ring worm that grows on and digests the warm moist skin between toes. cured by antifungal creams
29
what is direct transmission?
the pathogen is directly transferred from one individual to another
30
what is horizontal transmission?
transmission between two people
31
what is vertical transmission?
transmission between mother and unborn child
32
what is direct contact in animals?
•kissing or any contact with bodily fluids e.g many STDs
•direct skin to skin contact e.g. ring worm
•microorganisms from faeces transmitted onto hands
33
what is inoculation transmission?
•through a break in the skin e.g. HIV during sex
•from an animal bite e.g. rabies
•through a puncture wound/ sharing needles e.g. sepsis
34
what is ingestion transmission?
•taking in contaminated food or drink or transferring pathogens from hands to mouth e.g. cholera and diarrhoeal diseases
35
what is indirect transmission?
when the pathogen travels from one organism to another indirectly
36
what is fomites transmission?
inanimate objects such as bedding or socks can transfer pathogens such as athletes foot. e.g. lots of hospital acquired infections such as MRSA
37
what is droplet infection(inhalation)?
•minute droplets of saliva and mucus are expelled from your mouth as you talk, cough or sneeze. when breathed in people may become infected e.g. influenza
38
what is vector transmission in animal disease?
a vector transmits communicable pathogens from one host to another e.g. mosquitoes for malaria and water for cholera
39
what are factors affecting transmission of communciable diseases in animals?
•overcrowding
•poor nutrition
•compromised immune system
•poor disposal of waste causing vector breeding grounds
•climate change
•culture and infrastructure
•socioeconomic factors such as lack of trained healthcare professionals
40
what is direct transmission in plants?
direct contact of a healthy plant with a diseased plant e.g. TMV and ring rot
41
what is soil contamination (indirect plant)?
infected plants often leave infectious pathogens or spores in soil that can infect the next crop
42
what is vector transmission in plant disease?
•pathogens carried by wind
•water carrying spores and pathogens
•animals carrying spores and causing inoculation
•humans transmit pathogens to plants when farming
43
what are factors affecting transmission of communicable plant disease?
•planting varieties of crop that are susceptible to the disease
•overcrowding
•poor mineral nutrition (reduces resistance)
•damp and warm conditions increase fungal survival
•climate change
44
what are some common examples of physical barriers in plants?
•waxy cuticles
•bark
•cellulose cell walls of plant cells
45
why do plants not heal diseased tissue?
they seal it off and sacrifice it instead because they are constantly growing at the meristems
46
how do plant cells recognise an attack?
•receptors in the cells respond to molecules from the pathogens or to chemicals produced when the plant cell wall is attacked.
•this stimulates the release of signalling molecules
•this triggers cellular responses including producing defensive chemicals, sending alarm signals to to unaffected cells to trigger their defences and physically strengthen cell wall
47
how do plants strengthen their cell walls?
the polysaccharides callose and lignin are produced to strengthen it
48
what does current research suggest when looking at plant mechanical barriers?
•within minutes of an attack callose is synthesised and deposited between the cell walls and the cell membranes of cells next to infection site.
•this acts as a barrier preventing pathogens reaching the plant
•callose continues to be added alongside lignin making the barrier stronger
•callose blocks sieve plates in phloem
•callose is deposited in plasmodesmata between healthy cells infected cells
49
what do plant chemical defences do?
•repel insect vectors or kill invading pathogens
50
what are some examples of plant chemical defences?
•insect repellents such as citronella
•insecticides such as caffeine
•antibacterial compounds e.g. phenols and lysosomes
•antifungal compounds such as chitinases (enzymes that break down chitin in cell walls)
•anti oomycetes such as glucanases which break down glucans
•general toxins like cyanide
51
what are some different types of non specific human defences and how do they act as barriers?
•the skin covers the body and prevents pathogens from entering, it has a flora of healthy microbes which outcompete pathogens for space, skin also produces sebum which inhibits pathogenic growth
•many bodily tracts are lined with mucous membranes, mucus traps microbes and contains lysosomes to destroy bacterial and fungal cell walls, also contains phagocytes
•lysozymes in tears and urine and stomach acid also prevent pathogens getting into bodies
52
what is an active non specific defense?
•expulsive reflexes such as coughing and sneezing eject pathogen containing mucus
•vomiting and diarrhoea expel gut contents alongside pathogens
53
how do blood clots act as a non specific defense?
•platelets come into contact with collagen in skin through a wound and adhere to it closing off wound
•they also release thromboplastin, an enzyme which triggers a cascade of reactions resulting in the formation of a blood clot
•and serotonin which makes smooth muscle walls in vessels contract so they narrow and reduce blood supply to the damaged area.
•blood clots then dry into scabs allowing new epidermal cells to grow underneath
54
describe all the steps and chemicals in forming a clot.
•tissue is damaged activating platelets which release thromboplastin
•Ca2+ is a co factor to this enzyme and it catalyses prothrombin(1st reaction protein)
•this then turns into thrombin which catalyses fibrinogen into fibrin which holds platelets together into clot
55
what is the inflammatory response?
localised response to pathogens resulting in inflammation (pain, heat, redness, swelling of tissue)
56
how does the inflammatory response work?
mast cells are activated in damaged tissue and release histamines and cytokines
•histamines make blood vessels dilate causing localised heat and redness, to prevent pathogens reproducing
•histamines also make blood vessel walls leak more causing a swelling of tissue fluid (oedema)
•cytokines attract phagocytes to dispose of pathogens by phagocytosis
57
how do fevers act as a non specific defence?
cytokines cause hypothalamus to increase temperature
•this inhibits pathogen reproduction
•the specific immune system works better at higher temperatures
58
what are phagocytes?
specialised white cells that engulf and destroy pathogens. the two types are neutrophils and macrophages
59
what are the stages of phagocytosis for a neutrophil?
•pathogens produce chemicals that attract phagocytes
•phagocytes recognise the non human proteins
•the phagocyte engulfs the pathogen and encloses it in a vacuole called a phagosome
•the phagosome combines with a lysosome becoming a phagolysosome
•enzymes from lysosome digest and destroy pathogen.
60
what is a phagosome?
the vesicle in which a pathogen or damaged cell is engulfed by a phagocyte
61
what are the stages of phagocytosis for a macrophage?
•pathogens produce chemicals that attract phagocytes
•phagocytes recognise the non human proteins
•the phagocyte engulfs the pathogen and encloses it in a vacuole called a phagosome
•the phagosome combines with a lysosome becoming a phagolysosome
•enzymes from lysosome digest and destroy pathogen
•digested pathogen absorbed by phagocyte- antigens combine with MHC in cytoplasm
•MHC/antigen complex is displayed on phagocyte membrane making an antigen presenting cell (APC)
62
what is a major histocompatibility complex (MHC)?
special protein complex (glycoproteins on cell surface membrane)
63
how long does it roughly take a neutrophil to engulf and destroy a bacterium?
~10 minutes
64
what do cytokines do?
act as cell signalling molecules after a phagocyte has engulfed a pathogen informing other phagocytes that the body is under attack. they also can increase temperature and stimulate specific immune system
65
what do opsonins do?
chemicals that bind to pathogens and mark them so they can be more easily recognised by phagocytes
66
how long does the specific immune system take?
up to 14 days to first infection
67
what are antibodies?
y-shaped glycoproteins called immunoglobulins which bind to specific antigens on pathogen. there are millions of shapes to match all the different antigens
68
what is the structure of an antibody?
they are made of two identical long polypeptide chains called the heavy chains and two much shorter identical chains called the light chains. the chains are held together by disulfide bridges and there are also disulfide bridges within polypeptide chains holding them in shape
69
how do antibodies bind with antigen?
protein based complementary pairing. the binding site is an area of 110 amino acids on both heavy and light chains known as the variable region. it is a different shape on each antibody. the rest stays the same therefore being the constant region.
70
what does the hinge region of an antibody allow for?
flexibility, allowing it to bind to two separate antigens
71
how do antibodies defend the body?
(4 ways)
•the antibody in an antibody-antigen complex acts as an opsonin so the complex is easily engulfed and digested by phagocytes
•most pathogens can no longer invade the host cells once they are
part of an antigen-antibody complex
•antibodies act as agglutinins causing pathogen carrying antibody-antigen complexes to stick together
•antibodies can act as antitoxins binding to the toxins produced by pathogens and making them harmless
72
what is the specific immune system based upon?
specific b and t lymphocytes
73
where are b/t lymphocytes matured?
b in bone marrow
t in thymus gland
74
what are the 4 main types of t-lymphocyte?
•T helper cells
•T killer cells
•T memory cells
•T regulator cells
75
what do T helper cells do?
•they have surface CD4 receptors which bind to surface antigens on APCs
•they produce interleukins which are cytokines that stimulate the activity of b cells which increases antibody production, stimulates production of other T cells and attracts and stimulates macrophages to ingest pathogenic antibody-antigen complexes
76
what are agglutinins?
chemicals (antibodies) that cause pathogens to clump together so they are easier to digest
77
what do T killer cells do?
•destroy the pathogen carrying the antigen (cytotoxic cells)
•produces the chemical perforin which kills the pathogen by making the cell membrane freely permeable
78
what do T memory cells do?
•they live for a long time and are a part of immunological memory
•if they meet an antigen a second time they divide rapidly to form a huge number of clones of t killer cells
79
what do t regulator cells do?
•they suppress the immune system acting to control and regulate it
•they stop immune response once a pathogen has been eliminated and makes sure they body recognises self antigens and does not set up an autoimmune response
•interleukins are important in this control
80
what are the 3 main types of b lymphocyte?
•plasma cells
•B effector cells
•B memory cells
81
what is an autoimmune response?
•response when immune system acts against its own cells and destroys healthy body tissue
82
what do plasma cells do?
•produce antibodies to a particular antigen and release them into the circulation
•lives only a few days but releases ~2000 antibodies per second when active
83
what do B effector cells do?
•divide to form plasma cell clones
84
what do B memory cells do?
•live for a very long time and provide immunological memory. they are programmed to remember specific antigen and enable body to make a rapid response the next time the antigen is detected
85
what is cell-mediated immunity?
T lymphocytes responding to the cells of an organism that have been changed in some way e,g from a viral infection or mutation or transplanted cells
86
what are the stages of cell mediated immunity?
•macrophages digest pathogens and process their antigens forming APCs
•some receptors on some T helper cells will fit these specifc antigens and then become activated
•activated T helper cells produce interleukins which stimulate more T cells to divide by mitosis forming lots of identical cells
87
what is humoral immunity?
•body responding to antigens found outside the cells like bacteria
•it produces antibodies which are soluble in blood
•b lymphocytes have surface antibodies and a b cell with complementary antibodies to a pathogen will engulf it to become an APC
88
what are the stages of humoral immunity?
•activated T helper cells attach to B APC cells (clonal selection)
•interleukins produced by activated T helper cells activate the B cells
•activated b cells divide by mitosis to give clones of memory and plasma cells (clonal expansion)
•cloned plasma cells produce antibodies that fit the antigens on the surface of the pathogens which is primary immune response (days to weeks)
•B memory cells divide rapidly to form plasma clones if the same pathogen infects again (secondary immune response).
