communicable diseases 4.1 Flashcards
1
Q
what is a pathogen ?
A
a disease causing microorganism
eg. bacteria, viruses, fungi, pathogens
2
Q
what are bacteria ?
A
prokaryotes
no membrane bound nucleus or organelles
spherical, rod shaped, corkscrew shaped
a cell wall from peptidoglycan
they divide by binary fission
3
Q
what’s the difference between binary fission and mitosis ?
A
DNA replication occurs at the same time as DNA separation (no spindle)
4
Q
what are viruses ?
A
non living - doesn’t carry out life processes ( MRS GREEN)
50 times smaller than bacterium
use host cells to reproduce rapidly and evolve by developing adaptations to their host
many are pathogenic
5
Q
how does a virus infect a host cell to reproduce ?
A
- virus attaches to a specific host cell using surface proteins
- general material from virus is injected into host cell
- viral genes cause host cell to make new viruses by replicating DNA
- host cell splits open due to increased pressure and the new virus is released
6
Q
what is Protoctista ?
A
eukaryotic organisms
a small group of them are pathogenic - use a host organisms to their benefit
use a vector to transfer hosts
may enter body through water
7
Q
what is fungi ?
A
eukaryotic organisms
can live in the skin of an animal and it hyphae which form a network to grow under the skins surface
the reproductive hyphae grow to the surface of the skin to release spores, causing redness and irritation
not dangerous is animals but are in plants
cant photosynthesis, so they must digest nutrients extracellularly
saprophytes - feed on dead matter
8
Q
how do pathogens cause disease ?
A
damage host cells or tissues directly
produce toxins which damage host tissues
9
Q
what are exotoxins and endotoxins ?
A
exotoxins - produced and secreted by a normal pathogen
endotoxins - produced when a pathogen is damaged
10
Q
what is tuberculosis ?
A
bacteria
- effects humans and cattle
- damages lung tissue and supresses the immune system
- curable which antibiotics and preventable ( vaccination and improvement of living standards )
11
Q
what is ring rot ?
A
bacteria
- potatoes and tomatoes
- ring decay in vascular tissue and leaf wilting
12
Q
what is HIV/AIDS ?
A
virus
- targets T helper cells in the immune system
- no vaccine and no cure
13
Q
what is influenza ?
A
virus
- effects the ciliated epithelium cells in the gas exchange system
- it kills these cells leaving the airways open to secondary infection
14
Q
what is tobacco mosaic virus ?
A
virus
- effects tobacco plants and others
- spreads via plasmodesmata and phloem
- causes mottling of leaves
15
Q
what is black sigatoka ?
A
fungi
- effects bananas
- fungus attacks and destroys leaves
- hyphae penetrate and digest the cells, turning the leaves black
16
Q
what is athletes foot
A
fungi
- affects humans
- grows and digests the warm moist skin between toes
- causes cracking and scaling which is itchy and sore
- antifungal creams work to cure it
17
Q
what is potato / tomato late blight ?
A
Protoctista
- affects the tuber or fruit with necrotic brown lesions
- and lesions on leaves
18
Q
what is malaria ?
A
Protoctista
- spreads by mosquito vector
- invades liver cells, red blood cells and brain causing severe fever exhaustion and headaches
- no vaccine and no cure but preventative measures can control the vector ; remove standing water where they breed, mosquito nets and insecticides
19
Q
what’s direct transmission ?
A
the pathogen / disease is transmitted directly from one organism to another
eg. physical contact = touch, sexual intercourse
droplet infection = cough , sneeze
inoculation = break in the skin
ingestion = consuming contaminated food or drink
20
Q
how can the risk of direct transmission be reduced ?
A
- washing hands regularly
- keeping surfaces clean
- cleaning and disinfecting cuts
- sterilizing surgical instruments
- using condoms
21
Q
what is indirect transmission ?
A
when a disease is transmitted from one organism to another via an intermediate
fomites = inanimate objects that can harbour and transfer pathogens eg. clothing
vectors = an organism that spreads disease by carrying pathogens from one host to another host but is unaffected eg. mosquito
22
Q
how do living conditions affect transmission ?
A
-overcrowded living and working conditions increase transmission
-poor nutrition
-poor disposal of waste which provides breeding ground for vectors
23
Q
how do social factors affect transmission ?
A
- culture and transmission in some countries traditional medical practices can increase transmission
- socioeconomic factors - lack of trained health workers and insufficient education
24
Q
how does climate affect transmission ?
A
climate change - new vectors and diseases can emerge ; spread of malaria can increase
25
how can you prevent the spread of communicable diseases ?
- regular hand washing
- improvement of living and working conditions eg. reducing overcrowding, ensuring good nutrition, sterilisation
- effective disposal of bodily and household waste
26
how are diseases spread between animals and humans ?
zoonosis is an infectious disease that is transmitted from animals to humans eg. bird flu
people also act as vectors eg. foot and mouth disease
minimising contact with animals and washing hands thoroughly can prevent transmission
27
how are pathogens transmitted between plants ?
direct transmission = contact of a healthy plant and diseased plant
indirect transmission =
soil contamination eg. spores, bacteria, fungi or Protista remain in the soil
vectors eg. wind, water, animals and humas such as a former using infected tools on a healthy plant
28
how does fungi effect plants ?
it lives in the vascular tissue to acquire nutrients
the hyphae release extracellular enzymes eg. cellulases to digest surrounding tissue and cause decay
leaves will often become mottles in colour and shrivels before dying
fungal infection halts photosythesis
29
how is crop yield reduced due to fungi ?
fungal infection causes mottling and discolouration
photosynthesis is reduced
less carbohydrate is produced and so plants are smaller and fruit is smaller
yield is reduced
30
how do fungi reproduce when conditions are harsh ?
produced millions of spored which can spread huge distances this adaptation allows them to spread rapidly and widely through crops
31
how do pathogens reduce plant growth and yield ?
-reducing the rate of photosynthesis, blocking light or destroying chloroplasts
- increasing the rate of respiration as the plant fights the infection
- feeding of the plants sugars
- plants may water through wounds
- pathogens can block xylem and phloem
32
what factors affect the transmission of communicable diseases in plants ?
- planting crops that are susceptible in disease
- overcrowding
- poor mineral content of soil reduces their resistance to disease
- damp, warm conditions increases survival of pathogenic spores
- climate change : increased rainfall and wind promote the spread of disease, and new vectors can spread, drier conditions can reduce the spread of disease
33
how can farmers prevent the spread of communicable disease in plants ?
- leave plenty of space between plants to minimise contact
- clear fields thoroughly after harvesting
- rotate crops
- strict hygiene procedures ( washing boots, sterilising equipment ect. )
- control insect vectors
34
what are plants physical defences to pathogens ?
- cellulose cell wall and bark
- waxy cuticles ; preventing water collecting on cell surfaces to stop pathogenic growth
- lignin thickening of cell wall ; water proof
- stomatal closure when pathogenic organisms detected guard cells will close
35
what are plants chemical defences to pathogens ?
- terpenoids and phenois ; antibacterial and antifungal properties
- alkaloids ; nitrogen containing compounds- inhibit enzyme action or protein synthesis
- defensive proteins ; small, cysteine rich, proteins that are antimicrobial acting on plasma membrane
- hydrolytic enzyme found in the spaces between cells
36
how is an attack recognised ?
- receptors respond to molecules from pathogens/chemicals released when cell wall is attacked
- cell wall release signalling molecules which switch on genes in nucleus
- triggers cell responses ; producing defence chemicals, sending alarm signals to other cells , strengthening cell wall
37
what is put in place once the plant has activated it active defence ?
cell walls become thickened and strengthened with additional cellulose
deposition of cellulose between the plant cell wall and cell membrane near the invading pathogen (plasmodesmata)
an increase in production of defence chemicals
38
what is callose ?
large polysaccharide, deposited in sieve tubes blocking them so at the end of the growing season the pathogen cant spread
this forms a physical barrier
also blocks the plasmodesmata
can be deposited or removed through homeostatic function
39
what is tylose ?
balloon like swelling that fills xylem vessel, preventing spread of pathogen by blocking xylem
contains high conc of chemicals such as terbenes that are toxic to pathogens
40
what is a canker ?
a sunken necrotic lesion in woody tissue of plant caused by pathogens, results in death of cambium bark tissue
41
what is necrosis ?
deliberate cell suicide, a few cells are sacrificed to save the rest of the plant ( intracellular enzymes released )
42
what is a primary defence systems ?
a non specific defence against pathogens that is always present or rapidly activated
it responds to all pathogens the same way
43
how is the skin a primary defence in humans ?
physical barrier
contains keratin for strength
surface consists of hard layers of dead cells, sweat evaporates leaving salt behind
pH is slightly acidic due to fatty acids secreted
microorganisms outcompete pathogens for space
44
how is sebum a primary defence in humans ?
oily/waxy substance produced by sebaceous glands
coats and protects skin with antimycobacterial properties
45
how is hydrochloric acid a primary defence in humans ?
secreted by parietal cells of stomach
kills bacteria injected by food
46
how is mucus a primary defence in humans ?
secreted along length of gut to protect against acid enzymes and pathogens
made from glycoproteins molecules - sticky and slimy
cilia beat to move it along
lysozymes which destroy bacterial and fungal cell walls
contains phagocytes which remove pathogens
47
how are mucous membranes a primary defence in humans ?
produce mucous, line gut, respiratory system and reproductive system
epithelial cells interspersed with goblet cells that secret mucus
48
how are expulsive reflexes a primary defence in humans ?
sneezing, coughing when pathogens irritate the lining of airway and eject pathogens from the upper airway tract, this allows transmission of pathogens between hosts
vomiting and diarrhea expel gut contents to remove pathogens
49
how are lysozymes a part of the primary defence in humans ?
secreted by bodily fluids acts as antibacterial agent by breaking down bacterial and fungal walls
tears, sweat, urine, stomach acids, breastmilk , mucus and blood
50
why is is important to have bacteria in you ?
they outcompete pathogens and prevent infection from taking hold, they assist with digestion and production of some vitamins
51
how does blood clotting work ?
when the blood vessel is damaged, blood is exposed to collagen fibres
platelets stick to the exposed collagen forming a plug to stop bleeding
platelets become activated and release clotting factors
clotting factors convert prothrombin into active thrombin using vitamin k and calcium
thrombin catalyses the conversation of inactive soluble fibrogen into active insoluble fibrin
fibrin forms a mesh that traps red blood cells and strengthens the plug to form a clot
eventually the blood clot will be reabsorbed
52
how is a wound repaired ?
platelets release growth factors which stimulate stem cells
formation of new blood vessels
production of collagen fibres which are deposited
formation of granulation tissue which fills the wound
stem cells divide by mitosis and migrate over new tissue
wound contraction by contractile cells
death of unwanted cells
once epidermis has reached normal thickness scabs sloughs off
53
name two other primary non specific defences
ear canal - lined by wax which traps pathogens
female reproductive system - protected by mucus plug in the cervix during pregnancy and relatively acidic conditions in the vagina
54
what is a secondary non specific defence ?
act on pathogens that have entered the body
55
how does the body recognice invading pathogens ?
the antigen on the pathogen - normally a protein, polypeptide or polysaccharide
56
how are mast cells involved in allergic responses ?
antibodies to the allergen bind to the mast cells and the allergen together, this causes mast cells to release chemicals eg .histamines which cause allergy symptoms
57
what are the roles of opsonins ?
chemicals that bind to pathogens ( their antigens) to tag them , making them more recognisable to phagocytes
also act as binding sites for phagocytic cells to these can more easily bind and engulf the pathogen
58
how does a fever occur ?
when a pathogen invades you body , cytokines stimulates your hypothalamus to resent your body to a higher temperature
pathogens cant normally reproduce at higher than 37 degrees and the immune system works best at higher temp
59
what are the symptoms of immflamation ?
redness, pain, swelling, heat
it occurs because of cellular activity and chemical defences in the blood
60
what is the role of mast cells ?
they respond to damage by secreting histamine and cytokines
61
what does histamine do ?
is a cell signalling compound that causes increased blood flow through capillaries ( vasodilation )
capillaries become leaky allowing fluid, neutrophils, monocytes and some proteins to leave the blood and enter tissues causing swelling
62
what do cytokines do ?
attract phagocytes which leave the blood to enter tissues and engulf foreign material
63
what are the stages of inflammation ?
1. tissue is injured and bacteria enters wound site
2. the area becomes filled with tissue fluid that leaks out of the capillary into the area due to inflammatory factors
3. tissue cells release cytokines to attract phagocytes
64
what are the stages of phagocytosis ?
1. tissue cells release cytokines that attract phagocytes eg. neutrophils and macrophages
2. phagocytosis occurs when phagocytes recognise a pathogen as foreign or non self
3. phagocyte engulfs the pathogen forming a phagosome
4. the phagosome fuses with a lysosome to form a phagolysosome
5. the lysosome releases hydrolytic enzymes to digest and destroy the bacterium
65
what is lymph and its role with pathogens ?
- excess tissue fluid drains into the lymph vessels
- pathogens in tissue fluid can enter the lymph
- pathogens are transported along the lymphatic system to the nodes ( armpits ,neck, head ect)
- activity of phagocytes and lymphocytes cause swelling of the lymph nodes
66
what are the types of white blood cell (leucocytes) found in the blood and how can you tell them apart ?
monocyte - largest and have a kidney shaped nucleus , when they enter tissues they are called macrophage
lymphocyte - has a very large nucleus
neutrophil - has a lobed nucleus so they can squeeze through the pores of capillary walls
67
explain how a macrophage becomes an antigen presenting cell ?
1. monocyte is produced in bone marrow and travels through blood
2. moves into tissues and is called a macrophage
3. engulfs and digests a pathogen
4. combines the pathogens antigens with a glycoprotein called major histocompatibility complex (MHC)
5. the MHC moves the antigens to the macrophages own surface membrane
6. it is now an antigen presenting cell and can trigger the specific immune system
68
how is the specific immune system different to the non specific ?
targets a specific pathogen
slower to act in response to the first invasion
faster to react to the same pathogen infecting again due to memory cells
69
what does the cell mediated response target ?
pathogens that have invaded cells (virus), cells with mutations, antigen presenting cells , transplanted tissues by using highly specific cells
70
what does the humoral response target ?
pathogens in bodily fluids using antibodies
71
what are antigens ?
molecules ( polypeptides, glycoproteins ) on the surface of cells which the immune system can recognise as either self or non self
some toxins can also act as antigens
72
where do B lymphocytes and T lymphocytes mature ?
B - bone marrow
T - thymus gland
73
what are T lymphocytes ?
T cells gain specific receptors which are complementary to different antigens
they differentiate into T killer cells or T helper cells
there is lots of T cells with lots of different receptors and this allows them to recognise a wide variety of foreign antigens
74
explain the cell mediated immune response ?
1. macrophage destroys a pathogen by phagocytosis and displays antigens on its surface ( antigen presenting cell )
2. APC interacts with T helper cell and releases interleukin 1 which is a cell signalling molecule
3. interleukin 1 stimulates the T helper cell to release another cytokine : interleukin 2 which stimulates the growth of a T killer cell and binds to it
4. that process of activating a T cell is called clonal selection
5. T killer cells detect the antigen of the surface of infected body cells, they then produce and release perforin which forms pores in the membrane of the body cell
6. this causes water and ions to move into the cell and causes lysis
7. T memory cells are formed so if ever infected again with that specific antigen they are ready to respond
75
explain the humoral response ?
1. a macrophage destroys a pathogen by phagocytosis and the antigens are presented in its own cell membrane (APC)
2. the APC interacts with a specific T helper cell that has the complimentary receptor to the antigens
3. once bound the APC releases interleukin 1
4. interleukin 1 stimulates the T helper cell to release interleukin 2 which causes the B effector cells to differentiate into plasma cells
5. plasma cells divide by mitosis so they are clones
6. plasma cells makes large amounts of antibodies which destroy the pathogen by angulation or neutralisation
7. B memory cells are produced
76
what is clonal selection ?
where specific B or T helper lymphocytes are selected as they are complementary to the pathogen
77
what is clonal expansion ?
during B cell clonal expansion many copies of that B cell are produced that share specificity for the same antigen
78
what is the structure of an antibody ?
- 2 identical long/heavy polypeptide chains
- 2 identical short/light polypeptide chains
- identical chains are held together with disulphide bond
- at one end there is an antigen binding site / variable region with a unique shape and specificity
- other end is the receptor binding site
- the whole of the structure minus the antigen binding site is the constant region
- hinge region provides flexibility to allow for binding
79
what is an antibody ?
y shaped glycoprotein that binds to a specific protein or toxin
there are millions of different ones
highly specific to one antigen
80
what is neutralisation ?
antibodies can bind to antigens on the pathogens membrane and prevent it from attaching to and entering host cells. this encourages phagocytosis
81
what is agglutination ?
antibodies bind to antigens on surface of several pathogens, clumping them together. macrophages can recognise and easily destroy them by phagocytosis
82
how do antitoxins help to protect cells ?
antibodies can combine with toxins secreted by bacteria to neutralise them eg. tetanus
83
describe the primary immune response ?
antibodies are produced several days after infection
at this point the person is ill
antibodies and T killer cells will then remove the pathogen allowing recovery
84
describe the secondary immune response ?
larger , faster and longer lived
clonal selection occurs faster
- memory B lymphocytes are activated and divide into plasma cells that produce antibodies
- memory T lymphocytes are activated and dived into T killer cells to destroy cells with the antigen ( lysis )
85
why do vaccinations not cause illness ?
- attenuated version of the pathogen
- inactive form
- vaccine may not contain the entire pathogen but only its antigens
86
what are the different types of immunity ?
active - you immune system responds to the foreign antigens and makes antibodies
passive - your immune system does not respond to the antigens as you receive antibodies from a different source
natural or artificial
87
what is active natural immunity ?
eg. infection
occurs when you are naturally exposed to the antigen and your immune system responds and makes antibodies
88
what is active artificial immunity ?
eg. vaccination
you are provided with a vaccine that contains 1 or more pathogens ( immune system responds )
89
what is passive natural immunity ?
eg. maternal antibodies
antibodies can cross the placenta and through the breastmilk, the child only receives antibodies to antigens the mother has built immunity to
90
what is passive artificial immunity ?
eg. monoclonal antibodies
antibodies are injected or transferred into a person to provide them with instant immunity
91
how does active immunisation differ from passive immunisation in terms of antibody concentration ?
passive immunisation starts with a very high concentration of antibodies as they are given to the patient , this then drops rapidly
active immunisation starts to gradually increase in antibody concertation at the first shot and increases more rapidly after booster shots till the antibody concentration plateaus
92
what's the difference between vaccination and immunisation ?
vaccination is when a vaccine is administered to you ( injection ) but immunisation is what happens in your body after you have a vaccine
93
how does a vaccine work ?
1. vaccines contain antigens
2. the cells in the immune system recognise the antigens as non self and attack them
3. once the primary response has run its course memory cells are produced that will recognise the antigen in they ever come across it again
4. if there is a second infection the memory cells will produce plasma cells which release antibodies that bind to the specific antigen
94
what is in a vaccine ?
- whole live microorganisms with similar antigens to the real thing
- harmless or attenuated version of the pathogen
- dead pathogen
- a preparation of the antigens ( mRNA from the antigen )
- a toxoid ( harmless toxin )
95
what is herd immunity ?
when almost all the people in a community are vaccinated , this makes the disease extremely rare and those who are not vaccinated are protected
96
what are routine vaccines given ?
MMR - measles, mumps and rubella ( contains attenuated pathogens
meningitis C vaccine
polio vaccine
97
what can cause issues with vaccines ?
antigenic variation is when pathogens mutate and change their surface antigens and a new strain is formed
the vaccine cannot work against this as the memory cells will not recognise it and the primary response will be carried again
98
what is the difference between an epidemic and a pandemic ?
an epidemic is when an infectious disease spreads rapidly throughout a country or region
a pandemic is when the disease infects globally
99
what is an autoimmune disease ?
an abnormal immune response
antibodies attack self antigens
blood tests can show this
100
give an example of an autoimmune disease ?
rheumatoid arthritis
cause by cells of the immune system attacking cells in joints
- pain and inflammation
- joints are degraded
- feeling fatigued , movement is hard
101
what causes autoimmune diseases ?
not sure
genetic factors and environmental factors could both factor in
102
name sources of medicines
- accidental discovery
- traditional remedies
- observation of wildlife
- further plant research
- disease causing microorganisms
- personalised medicine
- some cancer drugs using soil bacteria / daffodils grown for a drug for alzimers
103
what problems do we face regarding future drug discovery ?
loss of biodiversity through the world , rainforests and coral reef, due to humans
its important to maintain biodiversity as any plant, animal or microorganism could be the key to a life saving drug
104
what are examples of common medicines ?
- painkillers
- anti-inflammatory
- anti-acid medicines
105
what are examples of medicines that can be used to cure people ?
chemotherapy
antibiotics
antifungals
106
when was penicillin discovered ?
1928 ( 20th centaury )
107
what is selective toxicity ?
antibiotics are able to interfere the metabolism of bacteria without affecting the metabolism of human cells
and therefore can inhibit or kill bacteria
108
what is personalised medicine ?
medicines that are tailored to a persons individual DNA by looking at genetic information to predict how you would respond to different drugs and only prescribe the one that is effective for you
109
how does antibiotic resistance develop ?
1. genetic variation in the population due to a mutation
2. a mutation may allow resistance
3. those without the resistance gene die which removes the competition
4. those with the advantageous allele survive and reproduce
5. allele becomes more common in the population
110
how can we avoid antibiotic resistance ?
- high standards of hygiene in hospitals and vulnerable areas
- minimizing the use of antibiotics and ensuring that every course is completed
