Health and Disease Week 20 Flashcards
(157 cards)
1
Q
What are properties of viruses?
A
- obligate intracellular
- host specific
- very small
2
Q
define obligate intracellular
A
has to live inside another organisms and cannot grow or replicate outside of its host
3
Q
How do viruses live?
A
they steal nutrients from the host to produce - they use the host to synthesise proteins
4
Q
Which 4 ways might a virus be classified?
A
- type of nucleic acid
- morphology
- the presence or absence of an envelope
- the host organism
5
Q
What are the 3 main classes of viruses (based on nucleic acid type)?
A
- DNA viruses
- RNA viruses
- RNA <=> DNA viruses (somewhere in between)
6
Q
What are the two types of DNA viruses?
A
ssDNA (single stranded) and dsDNA (double stranded)
7
Q
What are the 2 types of RNA viruses?
A
ssRNA and dsRNA
8
Q
What is the name given to a virus that uses the host cell to convert its ssRNA material into DNA material?
A
a retrovirus
9
Q
What is the name given to viruses that use the host cell to convert its dsDNA into into RNA?
A
hepadnaviruses
10
Q
What are the 2 main structures of viruses?
A
naked viruses and enveloped viruses
11
Q
What are the features of naked viruses?
A
- no outer membrane
- very simple structure
- essentially a shell of protein filled with nucleic acid
12
Q
What are the features of enveloped viruses?
A
- have an outer membrane
- the cell membrane is derived from the host cell
- they are modified with viral proteins for recognition and attachment to host cells
13
Q
What are the overall steps of viral multiplication?
A
- a virus particles attaches to its host cell
- the virus or its nucleic acid goes inside the host cell
- the virus uncoats and the capsid shell is removed either partly of fully
- the nucleic acid is now free inside the cell
- the nucleic acid and proteins are replicated
- they are assembled into virus particles
- released from the cell
14
Q
What are the 5 main steps of viral replication?
A
- attachment
- entry and uncoating
- synthesis of viral compounds
- assembly
- release
15
Q
How do viruses attach to their host cells?
A
they are not motile - so it occurs by random collision
16
Q
What must happen for a virus to attach to its host cell?
A
a specific interaction between the attachment site on the viral surface (e.g. a spike protein) and the receptor on the cell surface - very specific
17
Q
Which 2 methods are used for entry and uncoating?
A
endocytosis and fusion
18
Q
For which shape of virus does entry by endocytosis occur?
A
BOTH enveloped and naked viruses
19
Q
For which shape of virus does entry through fusion occur?
A
ONLY enveloped viruses
20
Q
What happens during uncoating?
A
there is full or partial shedding of capsid proteins
21
Q
What does the viral nucleic acid do inside the host cell?
A
compete with the host cell for control of biological machinery
22
Q
What happens during synthesis of viral components?
A
- the viral mRNA is produced
- mRNA directs the synthesis of early proteins
- early proteins then aid nucleic acid replication
- this allows synthesis of late proteins
23
Q
In which 2 ways is the nucleic acid assembled?
A
- packed into a preassembled capsid (capsid forms first then nucleic acid goes inside)
- it associates with the capsid proteins during formation (both happens at the same time)
24
Q
What are the 2 methods of release?
A
- cytolysis
- budding
25
How are viruses released by cytolysis?
the host cell bursts and releases all virus particles in one go
26
How are viruses released by budding?
membrane wraps around the virus particles and pinches it off - essentially the opposite to endocytosis
27
What are the 4 types of outcomes from viral infection?
1. cytocidal infection
2. chronic infection
3. latent infection
4. transforming infections
28
define cytocidal infection and give example
acute infections leading to lots of cell death - polio virus
29
define chronic infection and give an example
the cell death is slower, and the virus can be maintained for a very long time - hepatitis B virus
30
define latent infection and give an example
the infection hides for a while with no symptoms, and then something triggers the release of the virus - HIV, herpes simplex virus
31
define transforming infection and give an example
a virus that can cause cancer by insertion of an oncogene - human papilloma virus (HPV)
32
What are the steps of the life cycle of HIV?
1. HIV virus infects T helper cells
2. entry and uncoating
3. production of viral DNA by reverse transcriptase
4. this makes a DNA copy from an RNA molecule
5. the viral DNA gets integrated into the nucleus
6. something eventually triggers the release of viral DNA
7. viral DNA is released by budding
33
What are the 3 main types of viral vaccines?
1. live vaccines
2. killed vaccines
3. component vaccines
34
How do live vaccines work?
use attenuated strains
35
How do killed vaccines work?
using a virus killed by heat or chemicals
36
How do component vaccines work?
small parts of the virus are isolated from whole particles - for example, just 1 protein
37
What are the issues with component vaccines?
the single component may change in the virus - so no longer effective in the vaccine
38
What are the 3 types of modern vaccines?
1. vector vaccines
2. mRNA vaccines
3. DNA vaccines
39
How do vector vaccines work?
use a harmless virus to smuggle the instructions for making antigens from the disease-causing virus into cells
40
How do mRNA vaccines work?
the mRNA that encodes the antigen from the virus is introduced into a tissue and your own cells start to make the antigen - triggers the immune system
41
How do DNA vaccines work?
by introducing a plasmid that encodes the viral antigen into the host tissue
42
Which 2 main ways are used to produce virus particles?
cell cultures and embryonated hen's eggs
43
How are cell cultures used to produce virus particles?
1. infect the mammalian cell line with the virus
2. isolate and purify the virus particles produced
3. expensive fermenters used
44
define protozoa
a diverse group of single-celled 'animal-like' eukaryotes
45
How are embryonated hen's eggs used to produce virus particles?
1. the virus is injected into the fertilised chicken eggs
2. the virus is grown in the chicken eggs
3. the eggs are incubated for 2-3 days
4. isolate and purify the virus particles
46
Which group are protozoa a part of?
protists - this group includes protozoa, slime moulds, unicellular algae
47
Where are protozoa prevalent?
subtropical and tropical regions
48
How can protozoa infect tissues and organs?
- intracellular parasites inside cells
- extracellular parasites in the blood, intestines, urogenital system
49
How are protozoa transmitted?
by vectors or contaminated water, soil and food
50
What are the features of protozoa cells?
- plasma membrane
- pseudopodia
- nucleus
- ER
-golgi
- mitochondria
- food vacuole
51
What is the function of the pseudopodia?
they are extensions of the cell to aid movement
52
What is the function of the food vacuole?
this is where food is stored or degraded
53
What is the classification of protozoa based on?
shape/morphology
54
What are the 4 classes of protozoa?
1. amoeba
2. flaggellates
3. ciliates
4. apicomplexa (sporozoa)
55
What are features of amoeba?
- move by pseudopodia
56
What are features of flagellates?
- have flagella
- the direction of spinning due to the flagella determines which nutrients are available
57
What are features of ciliates?
- have cilia
- most are NOT pathogenic
58
What are features of apicomplexa (sporozoa)?
- they have a specific apical complex on the cell membrane used to invade other cells
- the are ALL parasitic
59
What is the main causative agent of malaria?
plasmodium falciparum
60
What is the life cycle of malaria?
1. the parasites are injected into the host along with the saliva of blood-feeding female mosquitos
2. plasmodium first moves to the liver and stays there for about 2 weeks
3. plasmodium is released from the liver
4. plasmodium then infects red blood cells repeatedly for days
5. mosquitos ingest the parasites with blood meal
6. parasites then go through a reproductive phase inside the mosquito and it becomes infective for other humans
61
What do infected liver cells do?
rupture and burst open to release merozoites, which penetrate more red blood cells
62
What are the 3 stages of uncomplicated malarial?
1. cold stage - shivering
2. hot stage - fever
3. sweating stage
63
What are the symptoms of cerebral malaria?
cerebral malaria - abnormal behaviour, seizures, coma
64
What are the symptoms of uncomplicated malaria?
headache, body ache, nausea, vomiting, enlarged spleen
65
What are the symptoms of complicated malaria?
shock, severe anaemia, liver failure, jaundice, ruptured spleen
66
define chemoprohphylaxis
preventing malaria through the use of drugs or chemicals
67
What drug are some malaria resistant to?
chloroquine
68
Which other drugs must be used for chemoprophylaxis in areas of chloroquine resistant plasmodium?
- mefloquine
- doxycycline
- atovaquone-proguanil
69
What are helminths?
parasitic worms
70
What are the features of helminths?
1. multicellular
2. have differentiated organs
3. no circulatory tract
71
What else do some helminths have?
suckers, hooks or plates at the anterior end that are used for attachment
72
Do helminths have their full life cycle in humans?
no
73
What is the life cycle of helminths?
1. they can produce eggs in humans
2. but they replicate free, in another host
74
Why is it difficult for the immune system to eradicate helminths?
they have a tough cuticle and some are camouflaged by coating with host molecules so hide from the immune system
75
What do parasitic helminths feed on?
body fluids or intestinal contents
76
What are the 3 main classes of worms that infect humans?
1. nematodes
2. cestodes
3. trematodes
77
What is another name for nematodes?
roundworms
78
What are the features of round worms?
1. long, cylindrical body
2. alimentary canal
79
What is another name for cestodes?
tapeworms
80
What are features of tapeworms?
1. flat, ribbon shaped
2. no digestive tract
3. its nutrients are absorbed through the cuticle
81
What is another name for trematodes?
flukes
82
What are the features of trematodes?
1. leaf-shaped
2. blind-branched alimentary tract
3. small
4. food goes in one way and comes out the same way
83
What is the latin name for large roundworms?
Ascaris lumbricoides
84
What is the major danger posed from Ascaris lumbricoides?
larvae may migrate to the lungs
85
What are symptoms of heavy infection with Ascaris lumbricoides?
abdominal pain, malnutrition
86
What are the symptoms of severe infection with Ascaris lumbricoides?
blockage of the intestines
87
What are the steps of the life cycle of Ascaris lumbricoides?
1. starts with adult worms in the small intestines
2. they produce eggs that are excreted in faeces
3. they go into the soil and develop
4. when fully developed and ingested, they initially go to the small intestine
5. the larvae hatch, and may these migrate to the lungs
88
What are blood and tissue nematodes called?
filariae
89
What is the life cycle of filariae?
1. adults in tissue or blood release larvae which are much smaller and circulate in the blood
2. they are taken up by a vector e.g. mosquito
3. the larvae develop in the vector and the vector can spread it
4. larvae gets into tissues and develop into adults
90
What is different about filariae compared to most roundworms?
need a vector to complete its lifestyle
91
What are 3 examples of disease caused by nematodes?
1. lympathic filariases
2. onchoceriasis
3. loiasis
92
What is another name for lympathic filariases?
elephantiasis
93
What does lymphatic filariasis cause?
damage to the lymphatic system and fluid build-up which results in the enlargement of the parts of the body and secondary infections
94
What is another name for onchocerciasis?
river blindness
95
What does onchocerciasis cause?
- microfilariae enter the internal tissues of the eye (except the lens)
- leads to inflammation, bleeding and blindness
96
What does loiasis cause?
- the adult Loa loa worm travels through the subcutaneous tissues
- causes inflammation of the skin and eyes
97
What is another name for cestodes?
tapeworms
98
How do cestodes infect humans?
when humans ingest a cyst
99
define cyst
the resting or dormant stage of a tapeworm
100
Where may cyst be ingested from?
undercooked meat or fish
101
Which type of helminth causes the largest number of deaths in humans?
trematodes
102
What organism do trematodes use as an intermediate host?
snails
103
Which pathogen causes schistosomiasis?
Schistosoma spp. (blood flukes)
104
What is another name for Schistosomiasis?
snail fever
105
What is the main route of contamination with Schistosomiasis?
drinking infected water as the eggs are excreted in faeces or urine
106
What are the initial symptoms of Schistosomiasis?
rash or itchy skin
107
What is the main damage caused by Schistosomiasis?
eggs getting stuck in tissues and subsequent response of the immune system - this causes organ damage due to inflammation and scarring
108
How is are intestinal nematodes/cestodes diagnosed?
- the eggs or laevae can be detected in faecal samples
- sometimes incidental diagnosis due to coughing up ascarids
109
How is Schistosomas (flukes) diagnosed?
eggs can be detected in faecal or urine samples
110
How are tissue nematodes diagnosed?
microfilaria in the blood
111
How may helminths be used as therapeutics in the future?
they are not cleared as they are able to modulate the immune system, and many studies have shown that NEMATODE infection protects against allergic diseases
112
What can GI nematodes do?
reduced skin reactivity to dust mite allergen
113
What is there an inverse correlation between?
incidence of asthma and hookworms
114
Which type of patients do fungal diseases mostly affect?
immune-compromised patients
115
What are the main features of fungi?
1. cell wall made of mainly beta-glucan and chitin
2. ergosterol in the cell membrane
3. reproduce by spores
4. eukaryotic
5. can be unicellular or multicellular
6. not susceptible to antibiotics
116
Which 4 areas are fungi important in? Why?
1. ecology - degrade organic matter
2. commercial - making bread, beer
3. pharmaceutical - create lots of enzymes, penicillin
4. pathogens - many different species
117
What are the 3 types of fungi?
1. yeasts
2. multicellular
3. macroscopic filamentous fungi
118
What is an example of a yeast?
Candida albicans
119
What is an example of a multicellular filamentous mould?
Trichophyton spp.
120
What is an example of macroscopic filamentous fungi?
mushrooms
121
What is the structure of the fungal cell wall?
- beta-glucan and mannan are linked by a number of proteins
- chitin is the thin layer above the cell membrane
122
How do yeasts reproduce?
by budding or fission
123
Describe budding
fungal cells grow bigger until they break off
124
How do moulds grow?
they grow as masses of overlapping and interlinking hyphal filaments - this forms a mycelium
125
define dimorphic
fungi that can switch between yeast and hyphal forms
126
How to myeliums grow?
cells are added at the tips of tubes - so hyphae grow at the tips
127
What are the 2 types of myelium?
septate and non-septate
128
define septate
mycelium that keeps its cell walls
129
define non-septate
mycelium that loses its cell walls
130
What can dimorphic fungi grow as?
yeasts or can form hyphae
131
What plays a role in determining the form of dimorphic fungi?
temperature and type of tissue - usually form hyphae at environmental temperature and grow as yeast cells in the body
132
What is an example of a dimorphic fungi?
Candida albicans
133
What disease does Candida albicans cause?
candidasis and thrush
134
What is Candidiasis?
when fungi gets into the lungs and infects lung tissue
135
How does Candida albicans cause Candidiasis?
1. yeast stage - fungus stays are yeast cells, usually in the gut
2. if there is damage to the intestine wall and the fungus gets into the blood, the candida can now form germ tubes
3. they may grow into a large fungal mass
4. gets into lungs and causes pulmonary candidiasis
136
define mycoses
diseases caused by fungi
137
What are the 3 categories of mycoses?
1. superficial and cutaneous mycoses
2. subcutaneous mycoses
3. systemic/deep mycoses
138
define superficial and cutaneous mycoses
when fungus grows on the body surface e.g. skin, hair, nails
139
What are examples of superficial/cutaneous mycoses?
Athlete's food, vaginal candidiasis
140
define subcutaneous mycoses
fungi infecting the deeper layers of skin, but it stays LOCALISED
141
What do subcutaneous mycoses feed on?
organic matter
142
What are these infections caused by?
traumatic inoculation - introduction of fungi through a wound or burn
143
define systemic/deep mycoses
fungal infections mainly through the lungs, but may spread to any organ
144
What are systemic/deep mycoses caused by?
inhalation of spores
145
Which type of patient is most susceptible to systemic/deep mycoses?
immune compromised patients - healthy patients have immune system to fight it off
146
Which type of fungus is Trichophyton spp?
mould
147
Which type of disease does Trichophyton cause?
cutaneous mycoses
148
What diseases does Trichophyton spp cause?
Athlete's food, ringworm, onychomyosis
149
What type of fungus is Candida albicans?
dimorphic
150
Which type of fungal disease does Candida albicans cause?
systemic or superficial mycoses
151
What are diseases caused by Candida albicans?
- oral/vaginal thrush
- nail and skin infection
- sepsis
152
define dermatophytes
a group of fungi that cause skin infections in humans
153
What is the main food source for dermatophytes?
keratin
154
How is infection with dermatophytes caused?
can be direct (human/animal contact) OR indirect (swimming pool, towels)
155
What do most antifungals act on?
the membrane lipid ergosterol
156
How do antifungals work?
1. can inhibit synthesis of ergosterol leading to accumulation of toxic sterol intermediates
2. OR they may bind directly causing leaky cells
3. may inhibit synthesis of beta-glucan for the cell wall
157
