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AS level biology > virus-detailed > Flashcards

virus-detailed Flashcards

1
Q

what is a virus?

A

a virus is a pathogenic particle which acts as parasite and capable of replication only within a host cell

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2
Q

what is a parasite?

A

organism that lives in or on a host

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3
Q

what does it mean by viruses are obligate intracellular organism?

A

carry out reproduction by parasitizing host cells

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4
Q

what is a host cell?

A

a living organism which provides food and shelter for growth of other organisms such as parasites

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5
Q

what is a vector?

A

living organisms that transmits the infectious agent such as virus from one infected organism to another

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6
Q

describe in detailed the structure of a virus

A
  • contains a nucleic acid core which could either be DNA or RNA
  • nucleic acid core contains virion associated polymerase which has a role in genome replicate and transcription
  • a protein coat called capsid protects the nucleic acid and together the protein coat and genome make up the nucleocapsid
  • the capsid is made up of protein sub unit, known as capsomeres
  • a phospholipid layer containing protein spikes for attachment on receptor of host cell
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7
Q

where exactly does the protein spikes of viruses attach to?

A

1- protein which act as receptor
2- lipids
3- carbohydrate chain found on glycolipid and glycoproteins

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8
Q

what is the typical size of a virus?

A

20 to 200 nanometer usually

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9
Q

what are the 2 main morphology of viruses and describe?

A

helical
-the capsomeres spiral up with the genome within the center

icosahedral
- contains 6 faces and protein spikes

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10
Q

what is a virion?

A

an infectious virus particle which is complete containing capsid, nucleic acid or even a phospholipid layer

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11
Q

what is a viral?

A

infectious agent which has a high level of redundancy

*2 or more genes perform the same biochemical function

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12
Q

what is a viroid?

A

an infectious virus particle which is in complete, only containing RNA without a protein coat

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13
Q

what is a proteolytic enzyme?

A

protease enzyme which break down or build up proteins

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14
Q

describe the general virus replication

A

1- virus attaches and enters host cell
2- disassembly of the virion occurs, revealing its nucleic acid, protein, etc
3- the viral genome enters the nucleus and gets
a}- replicated
b} Transcripted- DNA to RNA
4-the RNA, is translated outside the nucleus forming the virions proteins
5-the protein and replicated genome gets assembled to form more virions and is released

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15
Q

how does virus replication occur when using RNA

A

the RNA is injected into host and an enzyme known as reverse transcriptase, converts the RNA to DNA which can then be used normally in the steps of virus replication

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16
Q

what is the problem of RNA viruses such as HIV?

A

during the reverse transcription of RNA to DNA, the DNA is not checked for any mistakes, leading to mutations and variations between viruses

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17
Q

describe the lytic cycle{ active }

A

1- the virus binds to receptor of host cell and injects its viral genetic material into it
2-the viral genetic material takes over the host functions and starts transcribing and replicating its own DNA
3-once all the new materials are made, assembly of the new virion is made
4-due to increase in number of new virion, lysis of the cell occurs to release new viruses

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18
Q

what is the problem of cell lysis?

A

cells cannot survive without its cell membrane

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19
Q

what happens to other viruses inside the host cell when lysis occurs?
* host cell is multicellular

A

the virus can either use its own genetic material for replication or the new genetic material to infect other cells

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20
Q

describe the lysogenic cycle[ hidden]

A

1- virus attaches to the host cell and injects its genetic material
2-the genetic material stays hidden within the genetic material of the host cell
3- the host cell multiplies normally, replicating the viral DNA as well
4-a trigger such as lack of food for host cell or a chemical trigger occurs
5- the trigger causes the viral DNA to separate and go into the lytic cycle

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21
Q

in which cycle of replication can the host cell [in this case a microorganism one] be made more or less pathogenic [ cause disease]

A

in the lysogenic cycle/ hidden

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22
Q

what are the 5 phases and stages of replication and describe them

A

1- absorption- virus attachment
2- penetration-injection of genetic material
3- eclipse- starting of virus infection
4- doubling- replication of virus
5-virus exit phase-lysis of cell membrane

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23
Q

what are 4 examples of common viruses

A 
1- influenzas A virus
2- poliovirus
3-bacteriophages
4-HIV
5- hepatitis B virus
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24
Q

what is a cytopathic effect

A

structural change in host cell caused by viral invasion

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25
Q

which virus cause cells to become large granular clumps resembling bunch of grapes?

A

adenovirus

26
Q

which virus cause cells to become multi-nucleated?

A

herpes virus

27
Q

why do some cells become multinucleated as a cytopathic effect

A

1- fusion of cells

2- division of the nuclei

28
Q 
viruses which cause these transmission
1- respiratory transmission
2- faecal-oral route
3- blood-borne transmission
4-sexual transmission
A

1- influenza A virus
2-enterovirus[poliovirus]
3- hepatitis B virus
4- HIV

29
Q

What is virus tissue tropism?

A

the ability of a virus to infect specific cell tissue

30
Q

which cell does HIV infect?

A

CD4+{ a type of white blood cell}

31
Q

Which receptor does poliovirus attach to?

A

CD155

32
Q

What are 3 the classification of virus according to the host cell and describe them?

A 
1- animal virus: effects humans and animals
animal: chicken plague
humans; chicken pox, small pox
plants: virus that infects silkworm and butterflies
2- bacteriophages
infects and dissolve bacteria cells
3- plant virus: infect plants
eg; tabaco mosaic virus
33
Q

what is in vivo disease process?

A

research or work done within or on a living organism to study the disease process

34
Q

why are diseases caused by viruses?

A

1- cell destruction
*following an infection
2-virus-induced changes to gene expression
*inhibits gene expression in host cell
3- immunopathogenic disease
* viruses cause change of immune response

35
Q

what is gene expression?

A

process of turning on a gene in a cell to make RNA and proteins

36
Q

what is immunopathogenic disease?

A

process of disease development involving an immune response

37
Q

describe the way vaccines work

A

1- weakened form of pathogen injected into the body2- activation of the active immune systema}phagocytosis by phagocytesb}lymphocytes make antibodies
: antibodies attach to antigen on pathogens and destroy by alerting phagocytes or enzymic reaction
:lymphocytes remains as memory cell

38
Q

describe the 2 types of immunity

A

active immunity

  • developed after containing pathogen in the body
    eg: vaccination

passive immunity

  • provided by antibodies or antitoxins from outside the body
    eg: injection of antibodies or breast milk
39
Q

describe the acute virus infection graph

A

x-axis: time y-axis: amount of virus

  • as the time goes by and the amount of viruses increases, the symptoms increase slowly until an optimum and then decreases
  • the ending indicate that either host cell died or infection was resolved by innate immune response
40
Q

what are 2 features of acute virus infection?

A

1- localized to specific site of the body
2- development of viraemia with widespread infection of tissue
* viraemia-virus in the bloodstream

41
Q

describe virus induced tumor

A

1- virus enters uninfected cell
2- virus nucleic acid combines with cellular genome
3- virus genome takes over the cell
4- uncontrollable cell multiplication causing tumor formation

42
Q

what are ways for treatment and prevention of virus infection?

A

1- antivirals targeting

2- vaccination/immunization

43
Q

what are 4 antivirals target?

A

1- attachment prevention
2- nucleic acid replication prevention
3-virus protein process prevention
4- virus maturation prevention

44
Q 
what tumors do these viruses cause
1- human T-Cell leukemia virus [HTLV-1]
2- Epstein bar virus
3- human papillomavirus
4-hepatitis C virus
A 
1- leukemia
2- Burkitt's lymphoma
3-a} benign warts
    b} cervical carcinoma
4-liver carcinoma
45
Q

what are polioviruses properties

A

1- enterovirus
2- has an RNA genome
3- transmitted by fecal-oral route
4- causes poliomyelitis and gastrointestinal problems

46
Q

describe a poliovirus infection

A

1- virus enters the body via food and water
2- the virus enters guts
3- virus enters blood[ viraemia]
4- a]virus enters non-neuronal tissue
b] virus enters neuronal tissue
5- if virus enters neuronal tissue, paralysis occurs

47
Q

why does paralysis happens due to poliovirus entering the neuronal tissue?

A

never cells gets destroyed so muscles doesn’t receive signal from the CNS[ brain+ spinal cord]

48
Q

describe the incidence of poliomyelitis

A

x-axis; year y-axis; number of cases

  • the graph starts from the top and decrease,
  • the first decrease is by using inactivated vaccine and the greatest decrease is by using live weakened vaccine
49
Q

define inactivated virus

A

vaccine made from proteins or other small pieces of a pathogen

50
Q

what are the properties of Influenza A virus?

A 
1-myxovirus: any group of RNA viruses
2-enveloped virus
3- contains an RNA genome
4- infects animals and humans
5- undergoes antigenic variation
6- causes respiratory illness
51
Q

define antigenic variation

A

alteration of the protein or carbohydrate on infectious agents to avoid host immune response

52
Q

describe influenza A virus infection

A

1-spreads by respiratory route
2-infects cell in respiratory tract
3- respiratory epithelium gets destroyed
4- secondary bacterial infection

53
Q

what is secondary bacterial infection?

A

infection caused by bacteria after the treatment of the first

54
Q

what occurs in the secondary bacterial infection after influenza A virus infection

A

altered cytokine expression causing fever

55
Q

what is a cytokine?

A

a cell signaling molecule that help cell to cell communication in immune response

56
Q

what is an example of a cytokine?

A

1- interlukin-1

2- interferon

57
Q

what are the 2 types of generation of influenza A virus

A

1- antigenic shift involved

2-antigenic drift involved

58
Q

what is an antigenic shift?

A

mixing of genes from influenza viruses from different species

59
Q

what is an antigenic drift?

A

accumulation of minor genetic mutations

60
Q

describe the generation of influenza A virus involving antigenic shift

A

Human H2N2 gene and Avian H3N8 gene can go through a antigenic shift to form Human H3N2 gene

61
Q

describe the generation of influenza A virus involving antigenic drift

A

human H2N2 gene forms H2N2 gene However the HA and NA gene get mutated

AS level biology (20 decks)

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