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Microbiology > Virus' > Flashcards

Virus' Flashcards

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Biology 101 flashcards
1
Q

Why are viruses defined as obligate intracellular parasites

A

Viruses are defined as obligate intracellular parasites because they are unable to live independently and require a host. They are completely inert (dormant) when outside living cells

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2
Q

What is the basic and complex chemical composition of viruses

A

Basic - nucleic acid and protein

complex - nucleic acid, protein, lipid and carbohydrate

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3
Q

What is a viral nucleocapsid

A

RNA of DNA nucleic acid (genome) and capsid (protein coat)

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4
Q

What is a viral envelope

A

Envelopes are lipid bilayers which form when i virus buds out of a cell or through an intracellular membrane. Not all viruses contain an envelope

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5
Q

How are viruses classified (which characteristics)

A 
What kind of :
DNA or RNA
Symmetry 
Non/enveloped
single or double stranded 
plus or minus sense (if RNA)
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6
Q

What are the benefits of classifying viruses

A

Because similar viruses have similar features and characteristics and a new unknown virus which is extremely similar as a known virus could be treated and removed the same way.

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7
Q

What is the acronym for the 7 stages of Virus replication

A

Adders attack people unless sensible and relaxed

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8
Q

Describe the first two stages of virus replication

A

Adsorption - random non specific binding to cell surface

Attachment - viral surface ligand binds specifically to host cell receptor molecule (key and lock)

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9
Q

Describe third and fourth stages of virus replication

A

Penetration - completed by receptor mediated endocytosis or direct fusion of virus with plasma membrane
Uncoating - release of nucleic acid from capsid and lysosomal enzymes are released into cytoplasmic vacuoles.

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10
Q

Describe the 5th, 6th and 7th stages of virus replication

A

Synthesis - of viral protein and nucleic acid
Assembly - usually self assembly
Release - by budding or cell lysis

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11
Q

Describe two ways in which viruses are grown for experimental, industrial and diagnostic purposes

A

Experimental animals are used in virus research to study viral pathogenesis and host immune responses
Cell Cultures are used for virus isolation/identification and production

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12
Q

What is the incubation period of a virus

A

The time that the virus enters the cell to being able to observe clinical signs and symptoms

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13
Q

What is the period of infectivity

A

The period of infectivity is the period during which the individual can affect other people or animals

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14
Q

Define viral latency and what is recrudescence of latent virus?

A

Viral latency is the ability of a virus to live dormant in the cell, meaning once the cell is infected, the cell will never not be infected.
Recrudescence of latent virus is the reactivation of a virus from latency, generally associated with stress

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15
Q

Define the word pandemic

A

A pandemic is when a virus/disease affects a whole country or the world.

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16
Q

Define antiginic drift

A

Antigenic drift is a point mutation in amino acid changes the loops surrounding the receptor binding site of H or the catalytic site of N

17
Q

What is a viroid and how is it different to other ‘classical’ viruses

A

Virioid are infectious closed circle, single stranded RNA molecules with no protein that cause disease in plants

18
Q

Explain the possible benefits and costs of viral infection on plants

A

Viral infection on crop is responsible for huge losses and cannot be directly controlled by chemical application, transgenic resistance has shown promise but people skeptical over GMOs

19
Q

Explain the unique features of endogenous retroviruses

A

Endogenous retroviruses can become part of the ‘genetic dowry’ of the host. For example a cat becomes pregnant and the embyro is infected early, the virus remains dormant in genome. Kitten is born and thrives. The kitten then breeds and passes proviral DNA onto its offspring

20
Q

Define structure of bacteriophages and how it defines its replication strategy

A

Bacteriophages contain heads, tails and other components. When they latch onto a cell surface with their legs, their tail drills a hole into the cell and the nucleic acid in their head is released into cell

21
Q

Define the lytic cycle

A

The lytic cycle is where a phage enters a bacterium, takes over the bacterium to replicate lots of plaque and then kills the cell by making it explode (lyse)

22
Q

Define the lysogenic cycle

A

The lysogenic cycle is where a phage enters a bacterium and inserts its DNA into the bacterial chromosme, allowing the phage DNA (prophage) to be copied and passed on along with cells own DNA

23
Q

How can viruses be used as vectors in vaccine

A

Because viruses that attack an unfamiliar host will not infect it even if they are from the same family. Like how smallpox vaccine arised from cowpox.

24
Q

Explain the first line of defence in providing protection from infection

A

The first line of defense is
- skin - different tissue/epidermis to protect
- mucous membrane (respiratory tract) coughing sneezing and blocked nose
Gastrointestinal tract - stomach acid, mucus production and peristalsis
Actions - fever (increase temp of body to kill)

25
Q

Explain the second line of defense in providing protection from infection

A

The second line of defense is phagocytic white blood cells, antimicrobial proteins and the inflammatory response

26
Q

Explain the first line of defence in providing protection from infection

A

The first line of defence is
- skin - different tissue/epidermis to protect
- mucous membrane (respiratory tract) coughing sneezing and blocked nose
Gastrointestinal tract - stomach acid, mucus production and peristalsis
Actions - fever (increase temp of body to kill)

27
Q

Explain phagocytes in the second line of defence

A

phagocyte white blood cells eat foreign cells, they came in two types, neutrophils which are the first phagocytes at site of infection and if they eat foreign cell they blow up. And monocytes which morph into macrophages when infection progresses and are not suicidal. antimicrobial proteins and the inflammatory response

28
Q

Explain the term innate immunity

A

Innate immunity is immunity you are born with, the first and second lines of defence are innate immunity. Innate immunity is non specific and has no memory

29
Q

Explain the role of inflammation in second line of defence

A

Inflammation is like the internal fire alarm as it uses chemicals instead of sirens and instead of fire its swelling and redness. The purpose of inflammation is to destroy and confine infectious agent to stop spread and repair or replace tissue

30
Q

Explain the term adaptive immunity

A

Immunity that an organism develops over its life time, the third line of defence

31
Q

What is meant by the phrase humoral immunity

A

Humoral immunity involves production of antibodies against foreign antigens. The antibodies are produced by lymphocytes called B cells and the antibodies are called plasma cells, attacks cells in fluid of body not in cells

32
Q

What is meant by the phrase cellular immunity

A

Cellular immunity provides defence against bacteria and viruses that are inside host cells and inaccessible to antibodies

33
Q

Explain the cellular immunity (of 3rd line of defence)

A

Cellular immunity involves a specialised set of lymphocytes called T cells that recognise foreign antigens on surface of body cells. T(H) cell produces cytokines to stimulate other cell types. Activating the T(C) cell activates CTL which go on seek and destroy mission.

34
Q

Explain humoral immunity (of 3rd line of defence)

A

Humoral immunity involves use of B cells. The B cells interact with a possible pathogen, it checks with Th cell from cellular immunity to make sure pathogen is bad (clonal selection) and then cytokines stimulate the development of antibodies from B cell

35
Q

Explain what a active immunity is

A

Can be acquired naturally or artificially (vaccines) and the body generates an immune response to antigens and can be lifelong or temporal

36
Q

What is passive immunity

A

Can be acquired naturally (placenta) or artificially (antiserum) the immunity is only short lived. The host immunse system doesnt respond to antigen (venom)

37
Q

What is a killed whole virus vaccine

A

virus is killed by chemicals or heat (influenza virus vaccine)

38
Q

What is a subunit vaccine

A

Vaccine contains immunogenic peptide fragments of virus (hepatitis B vaccine)

39
Q

Define antigenic shift

A

Antigenic shift produces a HN subtype which occurs by mutation or genetic reassortment

Microbiology (12 decks)

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