Chapter 13/14: Viruses Flashcards Preview

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Flashcards in Chapter 13/14: Viruses Deck (45):
1

In its most simple form, a virus is composed of ____ ______ ______ __ _ ____ _____

Genomic material surrounded by a protein shell

 

 

Virus = "poison"

Virus particle also called virion

Virus size: 20 - 1000 nm

 

2

Genomic material

carries instructions for how to make more virus particles

 

3

Protein Shell

Protects the genomic material

Organized structure

4

A Virus Particle itself is inert

  • Doesn't reproduce, respire or divide by itself
  • Does not have an energy source
  • Does not have a way to make proteins
  • or any building blocks to make more proteins or genomic material

5

Viruses are an ________ _______ __________

Obligate intracellular parasite

 

must get materials from a cell

 

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6

Icosahedral

20 equal triangular faces

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7

Naked and Enveloped Viruses

Naked - spike proteins attach to host cell receptors in a specific manner

capsomers are protein subunits

 

Enveloped - the envelope is a lipid bilayer with proteins (spikes embedded in lipid bilayer)

derived from eukaryotic cells

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8

The eukaryotic cell is the ___ for animal viruses

Host

9

Animal Viruses

  • Vary by size, shape, envelope/naked, type of genetic material (DNA/RNA), and by transmission routes

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10

Steps of Virus Lifecycle

  1. Enter a cell
  2. Make more genomic material
  3. Make more protein
  4. Assemble protein and genomic material
  5. Exit a cell

11

Membrane Fusion (Enveloped)

Entry of enveloped animal viruses into host cells by membrane fusion - nucleic acid and capsid (protein coat) separate

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12

Endocytosis (Naked and Enveloped)

naked and enveloped animal viruses can enter the host cell by endocytosis, process in which the host cell "engulfs" the virus

Protein coat and nucleic acid are separated in the host

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13

The Viral Genome

  • may be DNA or RNA, not both; single stranded or double stranded
  • May be linear, circular or segmented
  • may be positive(+) strand RNA, negative(-) strand RNA, double stranded RNA, double stranded DNA
  • Life cycle is dependent on genome type

14

____ is required for translation

+mRNA

15

RNA animal viruses and their enzymes

  • RNA ----> RNA (RNA replicase)
  • RNA ----> ssDNA (Reverse Transcriptase)
  • RNA ----> dsDNA (Reverse Transcriptase)

 

 

THESE ENZYMES DO NOT HAVE PROOFREADING ABILITY AND MAKE MANY MISTAKES = MUTATIONS

Retroviruses

16

Which structures on a virus mediate attachment to host cells?

Spike structures

17

Do these structures bind to specific receptors or to any receptor

Specific receptors

18

HIV - human immunodeficiency virus

 

enveloped

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19

What is the genome of HIV composed of?

​RNA

20

What enzymes are required for the lifecycle of HIV?

  • Reverse transcriptase (RT)
  • Integrase (IN)
  • Protease (PR)

21

a RNA-dependent DNA polymerase; an enzyme that synthesizes a complementary DNA from an RNA template

Reverse Transcriptase

22

An enzyme produced by HIV that allows the integration of HIV DNA into the host cells DNA

​Integrase

23

An enzyme that digests protein

Protease

24

Which cells are targeted by HIV?

Helper T cells and Macrophages

25

Surface Glycoprotein (SU) gp120

spike protein that binds to the CD4 receptor on helper T cells and macrophages

26

Which enzymes/proteins/processes in the HIV lifecycle do anti- HIV medications target?

  • Targets the enzyme reverse transcriptase
  • targets protease
  • targets cell entry
  • integrase inhibitors

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27

Difference between HIV+ and AIDS

  • HIV+ has the HIV virus
  • AIDS must test positive for HIV virus and
  • have a CD4 T cell count of less than 200/mm^3 of whole blood or less than 14% CD4 T cells/total lymphocytes
  • CD4 T cell count of more than 200/mm3 and an opportunistic infection
  • develops when HIV has caused serious damage to the immune system

28

Influenza Virus

I

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29

What is the genome of influenza?

8 separate strands of RNA

30

_____ _____ is required for replication of the influenza genome

RNA replicase

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31

is the reason for new influenza strains each year

Antigenic drift (point mutations)

32

can give rise to completely new H and N proteins, thus leading to potential epidemics

Antigenic shift (from reassortment)

33

​Influenza Strains

  • based on their hemagglutinin (H) protein and their neuraminidase (N) protein; the different numbers associated with the H and N indicate different H and N proteins
  • antibodies are specific to specific flu strains 

34

Exit a cell 

Release of envelope viruses by budding

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35

Types of Infections

  • Carriers: persons with or without disease symptoms who shed the virus

36

​Acute Infections

  • self-limited diseases in which the virus often remains localized
  • short duration
  • mumps, measles, influenza, polio

37

Persistent infections

  • Virus establishes infection that remains for years or even life, often without disease symptoms
  • Latent - symptom-less period followed by reactivation, can detect infection only during reactivation period
    • ex. herpes, chickenpox (reactivates as shingles)

 

  • Chronic - infectious virus present at all times
    • ex. hepatitis B virus is continually produced in carriers
  • Slow - infectious agent gradually increases in amount over a very long time; often there are no symptoms
    • ex. HIV

38

Human Herpes Virus

  • Herpesviridae family is very large with 100 different viruses
  • double-strand DNA genome, enveloped with surface projections
  • the shapeless tegument consists of viral enzymes
  • latent infection

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39

Hepatitis

  • hepatitis - liver inflammation - symptoms are fatigue, fever, loss of appetite, nausea, right-side abdominal pain, dark urine, clay colored feces, jaudice
  • 6 different viruses/diseases: Hepatitis A, B, C, D, E, G
    • B virus: dsDNA genome
    • C virus: ssRNA genome

40

Human Papilloma Virus (HPV)

most common sexually transmitted disease - 40 million Americans

diagnosed by looking for abnormal cells in pap smear

41

What is cancer

Uncontrolled cell growth and spread

42

relentlessly growing mass of abnormal cells, ​our cells

Tumor

  • Benign Tumor : localized tumor
  • Malignant Tumor : metastasized (spreading) tumor

43

HPV and cervical cancer

HPV is a major cause of cervical cancer

12,500 cases each year with 4,500 deaths

44

​Antivirals

  • antibiotics don't work against them (no cell wall or ribosomes)
  • most anti-virals are against a specific virus
  • no anti-virals can eliminate latent viral infections
  • Anti-virals typically work against virus-encoded enzymes
  • often becomes resistant to drugs due to mutations
  •  

45

Differentiation of bacteria and viruses experimentally

  • Filtration: viruses pass through .2 micron filters, but bacteria do not
  • microscopy: bacteria are visible through light microscopes, but viruses are not; use electron microscope
  • antibiotics: bacteria are susceptible to antibiotics, but viruses are not
  • independent growth: bacteria are able to grow/reproduce on their own, but viruses need animal hosts and are thus cultured via tissues