Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

IMMUNOLOGY (foundation B) > 37. Biological threats to the body - VIRUSES > Flashcards

37. Biological threats to the body - VIRUSES Flashcards

1
Q

VIRUSES are OBLIGATE INTRACELLULAR PARASITES meaning

A

they MUST be able to get INSIDE the HOST CELL in order to REPLICATE and have an EFFECT

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

all VIRAL GENOMES/VIRUSES can ONLY FUNCTION when and how

A

after they are REPLICATED IN a CELL

must make mRNA that can be TRANSLATED by HOST RIBOSOMES
- HIJACK HOST PROTEIN SYNTHESIS MACHINERY to make viral proteins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

FEATURES of a VIRION (VIRUS PARTICLE)

A
  • VIRAL GENOME / NUCLEIC ACID
  • viral genome surrounded and protected by PROTEIN SHELL - CAPSID
  • some have Viral ENVELOPE
  • envelope PROTEINS (glycoproteins)
  • virus PROTEINS
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

not all VIRUSES have…

A

ENVELOPES

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

2 terms in grouping viruses together

A
  • CLASSIFICATION : determining the evolutionary relationships between organisms
  • TAXONOMY: assigning scientific names according to agreed international scientific rules
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

how are VIRUSES GROUPED (5)

A

ORDER
FAMILY (generally use family name)
SUB-FAMILY
GENUS
SPECIES (then talk about individual species)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Why is it important to be able to CLASSIFY viruses?

A

Classification makes possible PREDICTIONS
about the PROPERTIES of a virus.
e.g. replication, structure, pathogenesis & transmission

Particularly important when a NEW VIRUS is INDENTIFIED

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What PROPERTIES are used for CLASSIFICATION

A
  • SIZE of VIRION and CAPSID
  • PRESENCE or ABSENCE of ENVELOPE
  • SYMMETRY of CAPSID (protein shell)
  • NATURE and SEQUENCE of VIRAL GENOME/NUCLEIC ACID
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Another way of GROUPING viruses is based on
the… (2)

A
  • SYMPTOMS
  • ROUTE of TRANSMISSION
    eg Respiratory viruses
    Arboviruses (mosquitos)
    Blood borne viruses
    Enteric viruses
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

VIRUS INFECTION CYCLE - 6 STEPS

A
  1. ATTACHMENT of virus to receptors on host cell
  2. PENETRATION - releases capsid
  3. UNCOATING of CAPSID to release genetic material
  4. REPLICATION
    synthesis of viral mRNA, viral protein for new capsids, viral nucleic acids (new genome)
    - to form new viruses
  5. ASSEMBLY of the new components
    capsids form around nucleic acid
  6. RELEASE of new viruses
    by BUDDING or CYTOLYSIS
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

NEW VIRUSES can be RELEASED from host cell in 2 ways:

A
  • BUDDING
    takes membrane from cell and FORMS ENVELOPE
  • CYTOLYSIS
    BREAKS CELLS OPEN
    no envelope
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

how is BACTERIAL REPLICATION

A

by BINARY FISSION - DIVISION
(like human cells)

EXPONENTIAL GROWTH
2 - 4 - 8.. etc

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

how is VIRAL REPLICATION as opposed to bacterial

A

after entering cell, virion is DISASSEMBLED so NO /few infectious VIRUS DETECTED

  • when all new components are made, NEW VIRUSES FORMED and RELEASED - can be DETECTED

EXPONENTIAL BURST
sudden increase from few to very many

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

VIRUS GENOMES can be either (5)

A
  • DNA or RNA
  • DOUBLE-STRANDED (ds) or SINGLE-STRANDED (ss)
  • if SINGLE-STRANDED either POSITIVE or NEGATIVE sense
  • LINEAR or CIRCULAR
  • SINGLE genome or SEGMENTED (More than 1)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

SINGLE-STRANDED VIRAL GENOME can be either…

A

POSITIVE or NEGATIVE

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

VIRUS GENOMES RANGE in SIZE
but relative to BACTEREIAL GENOMES and HUMAN GENOMES…

A

significantly SMALLER

largest viral: Herpesviruses 120-240 thousand bases
smallest viral: HIV 9750 bases

HUMAN CHROMOSOMES
smallest: 47 million
largest: 247 million basepairs

17
Q

VIRAL GENOMES have to be able to MAKE

A

mRNA

– to be translated by ribosomes to make viral protein
– to make new virus particles (virions)

18
Q

what is BALTIMORE CLASSIFICATION

A

– based on mRNA as the common theme

– viruses (genomes) classified depending on HOW
they MAKE mRNA (+ve sense )

19
Q

how many CLASSES of VIRAL GENOMES

A

7

ds DNA
ss DNA

ds RNA
ss RNA (+)
ss RNA (-)

ss RNA (RT)
ds DNA (RT)
(retro-transcribing)

ALL MAKE mRNA in SPECIFIC WAY

20
Q

modes of VIRAL TRANSMISSION (5)

A
  • RESPIRATORY
  • ORAL/FAECAL
  • BLOOD BORNE viruses
  • other BODY FLUIDS
  • ARBOVIRUSES - via VECTOR eg mosquito
21
Q

what are the 2 periods in VIRAL INFECTION

A
  • INCUBATION PERIOD
  • INFECTIOUS PERIOD
22
Q

what is the INCUBATION PERIOD

A

the period BETWEEN when you are FIRST INFECTED with the virus, the virus is REPLICATING

23
Q

what is the INFECTIOUS PERIOD

A

The period when you are RELEASING VIRUS which
can INFECT OTHERS
- CONTAGIOUS period

24
Q

INCUBATION time, INFECTIOUS period, SYMPTOMS

example INFLUENZA

A
  • INCUBATION time UPTO 7 DAYS(normally 2 -3)
  • SYMPTOMS VARIES
  • INFECTIOUS BEFORE SYMPTOMS show and AFTER
    SYMPTOMS fade
25
Q

INCUBATION time, INFECTIOUS period, SYMPTOMS

example ROTAVIRUS

A
  • INCUBATION time around 2 DAYS
  • SYMPTOMS UPTO 8 DAYS
  • INFECTIOUS AFTER 2 DAYS, and can be for a DAY
    OR TWO AFTER SYMPTOMS fade
26
Q

how do you MEASURE HOW CONTAGIOUS viruses are

A

BASIC REPRODUCTIVE NUMBER R0

A means of expressing how many uninfected people can be infected by one infectious person

i.e. how well the virus SPREADS in a population

27
Q

what does R0 <1 mean

A

the infection will generally DIE OUT in the population

(1 infected individual can infect less than 1 unaffected person)

28
Q

what does R0 >1 mean

A

the infection will be MAINTAINED and SPREAD in the population

(1 infected individual can infect more than 1 unaffected person)

29
Q

A high R0 means…

A

the virus will spread quickly

30
Q

HOST DEFENCE MECHANISMS in immunological responses (4)

A
  1. ANATOMICAL and CHEMICAL - PHYSICAL BARRIERS
    - Skin, mucous, tears,saliva, stomach acid
  2. INTRINSIC
    - IMMEDIATE, NON-SPECIFIC
    - ALWAYS PRESENT in (un-infected) cells such as
    autophagy/apoptosis/RNA silencing/anti-viral
    proteins/recognition of invading pathogen
  3. INNATE immunity
    - IMMEDIATE (but needs to be switched on)
    - key to recognising presence of virus
    - Induced by the presence of infection
    - e.g. NK cells/Complement/Cytokines
  4. ADAPTIVE immunity
    - SPECIFIC but slow
    - T and B cells
    - generating memory
31
Q

what is PATHOGENESIS

A

mode of production or development of disease

HOW viruses CAUSE DISEASE

32
Q

what is VIRULENCE

A

the CAPACITY of a virus to PRODUCE DISEASE in a host

33
Q

you can think of VIRAL PATHOGENESIS in 2 ways:

A
  • The EFFECT of the virus REPLICATING in the host
  • The EFFECT of the IMMUNE RESPONSE

(The combined process occurring during viral infection - COMBINED EFFECT)

34
Q

Do all viruses infections cause (noticeable)
disease?

A

NO
- subclinical infections (asymptomatic)

35
Q

what is a SYSTEMIC INFECTION

A

SPREAD of virus THROUGHOUT the BODY

MULTIPLE ORGANS INFECTED

(Localised infection: replicate locally, doesnt spread)

36
Q

define VIRAEMIA

A

the existence of VIRUSES/virus particles IN THE BLOOD STREAM

37
Q

what can you get from SYSTEMIC INFECTION

A

Virus gains ACCESS into the BLOOD STREAM (lymphatic system).
- VIRAEMIA

Extremely RAPID virus DISSEMINATION (spread) THROUGHOUT the BODY

38
Q

describe LYTIC and LATENT INFECTION

A

1ST : LYTIC
virus REPLICATING
SYMPTOMS of disease

virus production levels fall to 0 (immune response)

LATENT PERIOD
- virus still PRESENT but DORMANT
SILENT - no symptoms

some signal may cause REACTIVATION
LYTIC period again
- not always associated with symptoms
- virus production doesn’t often reach same levels

IMMUNOLOGY (foundation B) (7 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions