Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

MED-109 Biology II > Topic 9: viruses > Flashcards

Topic 9: viruses Flashcards

(81 cards)

Start Studying
1
Q

Describe viruses

A
  • Non-cellular infectious particles
  • No cells
  • Smaller than bacteria
  • Size = 10-300 nm diameter
  • Visualized via EM
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Define obligate intracellular parasites

A
  • Depend on host cell for replication
  • Use enzymes of host to replicate
  • Infect eukaryotic/prokaryotic cells
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Define bacteriophages

A

Virus that infect bacteria

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

Describe the structure of viruses

A

1) Nucleic acid = DNA/RNA
2) Capsid = protein coat
3) Envelope = only present in some

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

Describe function of capsid

A
  • Encloses + protects genome from nucleases
  • Have fibers assisting attachment of virus > host cell
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Describe envelope

A
  • Consists of membrane
  • Carries glycoproteins
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Types of viral genomes

A

1) Double/single-stranded DNA
2) Double/single-stranded RNA

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

2 types of viruses

A

1) DNA viruses
2) RNA viruses

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Describe the structure of capsid

A
  • Made of = protein subunits = capsomeres
  • Shape/symmetry = variable
    1) Icosahedral/spherical symmetry
    2) Helical symmetry
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Describe the structure + function of envelopes

A
  • Have membranous envelope around capsid
  • Function = help virus infect host = fuses to host membrane
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Explain the origin of envelopes

A
  • Derived from host cell membrane
  • Form during exit of viral particle from host cell
  • Viral glycoproteins bind to receptor on host cell
  • Contain = viral + host cell molecules
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Describe the structure of bacteriophages

A
  • Shape = spherical/helical
  • Capsid head = encloses nucleic acid/DNA
  • Protein tail = fibers help attach phage to host
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Describe the features of viral replicative cycle

A
  • Attachment + entry to host = virl particle + genome enter cell
  • Virus replication = use host machinery to replicate genome > viral proteins
  • Assembly + release = nucleic acid molecules + capsomeres spontaneously self assemble = new virus > releases from cell
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Give the 8 stages of replicative cycle

A

1) Attachment
2) Penetration of virus into cell
3) Uncoating of genome
4) Replication
5) Gene expression
6) Assembly
7) Release
8) Maturation = only for envelopes viruses

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What causes variation in the cycle?

A
  • Depending on nucleic acid
  • If enveloped/non-enveloped virus
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Describe attachment

A

ENVELOPED:
- Glycoprotein on viral envelope attach on receptor on plasma membrane of host
NON-ENVELOPED:
- Fiber/spikes on capsid attach to host membrane receptors

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Describe penetration

A

ENVELOPED:
- Membrane fusion of envelope + host membrane
NON-ENVELOPED:
- Via endocytosis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Describe uncoating

A
  • Capsomeres fall apart
  • Catalyzed by lysozyme
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Describe replication

A
  • Replication of viral genome in host
  • Production of new viral proteins
  • Different replication mechanisms = based on genome type = ds/ss DNA / ds/ss RNA viruses
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Give the ss RNA viruses

A
  • Positive sense RNA genome 5’-3’ RNA
  • Negative sense RNA genome 3’-5’ RNA
  • Retrovirus
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Explain replication of DNA viruses

A
  • Same mechanisms as host
  • Single/double-stranded DNA replicates using = host DNA polymerase
  • Viral DNA > Viral cDNA
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Explain replication of RNA viruses

A
  • Different mechanism than host
  • Retroviruses = use viral enzyme = reverse transcriptase > host RNA polymerase
  • Viral RNA > Viral cDNA > Viral RNA copy
  • Other RNA viruses = use viral enzyme = RNA dependant RNA polymerase = replicate
  • Viral RNA > Viral RNA copy
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Describe the transcription/translation of viral nucleic acid to proteins in DNA

A
  • Viral DNA > Viral nRNA via host RNA polymerase
  • Viral DNA + host RNA polymerase + transcription > viral mRNA + ribosomes + translation > viral proteins
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Describe the transcription/translation of viral nucleic acid to proteins in RNA

A
  • Viral RNA acts as = mRNA / template for production using viral RNA dependant RNA polymerase
  • Viral mRNA translated > viral proteins via host’s ribosomes + machinery
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Define host DNA polymerase
- DNA dependant DNA polymerase - Uses DNA as template =synthesize new DNA strand
26
Define host RNA polymerase
- DNA dependant RNA polymerase - Uses DNA > synthesize RNA
27
Define viral RNA polymerase
- RNA dependant RNA polymerase - Use RNA > synthesize RNA
28
Define viral reverse transcriptase
- RNA dependant DNA polymerase - Use RNA > synthesize DNA
29
Explain assembly
- Viral proteins = capsomers = assemble > produce new capsid - Capsid encapsulates new viral genome = new viral particles
30
Describe release
NON ENVELOPED: - Via lysis of host ENVELOPED: - Via budding = need maturation for this - Host cell destroyed via = change in permeabiliy + inhibition of host gene expression
31
Why is retrovirus replicative cycle special?
- Single-stranded RNA virus uses reverse transcriptase > RNA genome > DNA - Exception to central dogma of genetic info transfer - RNA > DNA > RNA > protein - E.g. HIV
32
Describe the replicative cycle for retrovirus
ATTACHMENT + ENTRY: - viral glycoprotein binds to host receptor REVERSE TRANSCRIPTASE: - Viral enzyme converts RNA > cDNA INTEGRASE: - Viral enzyme integrates viral + host genomes - cDNA inserted at random into host genome = provirus TRANSCRIPTION: - Host RNA polymerase proviral DNA > RNA VIRAL RNA: - Acts as mRNA to synthesize to viral proteins - Acts as genome for new virus released from cell PROTEASE: - Viral enzyme cuts viral polypeptide produced via translation - Assembly + release from cell
33
What are the 2 replicative cycles of phages
1) Lytic cycle = causes cell lysis 2) Lysogenic cycle = cell not destroyed
34
Explain the lytic cycle
- Host cell membrane breaks = new phages released = death of host - Virulent phages = only produced via lytic cycle
35
Explain lysogenic cycle
- Genome replicates without destroying host - Viral DNA incorporated into host chromosome = integrated viral DNA = prophage - Host cell division = phage DNA copied + passed to daughter cells - Environmental signal = trigger virus genome > exit bacterial chromosome = switch to lytic mode - Temperate phages = replicate via lytic + lysogenic cycles
36
What are the bacterial defences against phages?
- Bacterial restriction enzyme = recognize + cut up phage DNA
37
Explain the origin of viruses
- Nucleic acid fragments released from cellular organisms - Genome sources = plasmids/bacterial + yeast DNA/transposons - Not sure if they evolved pre/post cells
38
Give the 4 mechanisms which viruses kill host cells with
1) Release of hydrolytic enzymes from lysosomes = lysis 2) Cause cell to produce toxin = disease symptoms 3) Toxic macromolecules + change permeability of membrane 4) Inhibit host cell replication machinery
39
Define vaccines
- Derivatives of pathogenic microbes/ viruses = stimulate immune system = defenses against hamful pathogens - Dead/inactive pathogen/product
40
What is the function of vaccines?
- Prevent some viral illnesses - Important control measure = viral infections can't be treated with antibiotics - Antivirals can treat not cure - Disease eradication via systematic vaccine campaigns e.g. smallpox
41
Define emerging viruses
- Suddenly become apparent
42
Give examples of emerging viruses
- 2009 flu outbreak = pandemic = influenza virus strain H1N1 - COVID-19 pandemic = coronavirus SARS-CoV-2 - Flu epidemics are caused by new strains of influenza = people have little immunity
43
What causes emerging viruses?
- New diseases emerge = virus spreads from animals - Viral strains jump species = exchange genetic material with virus humans have no immunity - New strains = pandemics - E.g. 2009 flu pandemic = pigs > humans
44
What does SARS-CoV-2 stand for?
Severe acute respiratory syndrome coronavirus 2
45
Describe SARS-CoV-2
- Enveloped positive-sense ssRNA virus - 7th coronavirus to infect humans - 3 caused serious respiratory diseases + 4 cause common cold - Originated in Hubei China Dec 2019 - Zoonotic origin - More than 704 million cases + >7 million deaths
46
Describe zoonotic origin of SARS-CoV-2
- Passed from bats via intermediate to humans - Enters human cells via binding angiotensin receptor = converts enzyme 2
47
Give the 3 approved antiviral drugs
1) Remdesivir 2) Molnupiravir 3) Paxlovid = Nirmatrelvir + Ritonavir
48
Describe the symptoms + complications of COVID-19
SYMPTOMS: - Fever - Cough - Fatigue - Shortness of breath - Loss of smell/taste - Sputum production - Muscle + joint pains COMPLICATIONS: - Pneumonia - Multi-organ failure - Cytokine storm
49
Describe the transmission + diagnosis of COVID-19
TRANSMISSION: - Air-borne DIAGNOSTIC METHODS: 1) Real-time reverse transcription polymerase chain reaction = rRT-PCR = from nasopharyngeal swab = viral RNA detection 2) Antigen tests = rapid/self test = nasopharyngeal swab = viral antigen detection
50
Describe how RT-PCR works
- Viral RNA + reverse transcriptase > cDNA + DNA polymerase > cDNA = 35-40 copies - PCR = amplifies viral cDNA = highly sensitive
51
What is the case fatality rate for COVID-19
1%
52
What are the 3 treatments for COVID-19?
1) Antiviral drugs: - Remdesivir + Molnupiravir + Nirmatrelvir/Ritonavir 2) Anti-inflammatory drugs: - Dexamethasone = costocosteriod + immunosuppresive = patients with oxygen support only 3) Neutralising antibodies: - Mimic immune system + attack virus = non- hospitalized high risk patients only
53
Give the 4 different vaccines for COVID-19
1) Pfizer/Moderna = mRNA vaccines 2) Novavax = protein subunit 3) J&J/Astra xeneca = vector vaccine 4) Valneva = whole inactivated virus
54
What viruses cause common cold?
- Adenovirus - Coronavirus - Rhinovirus - Enterovirus
55
Give the 2 types of Herpes viruses
1) HSV-1 = oral infection 2) HSV-2 = genital infection
56
Give the symptoms for Varcella zoster virus
- Causes chickenpox = children - Shingles = adults
57
Give the symptoms of Epstein-Barr virus
- Causes infectious mononucleosis - Causes Burkitt's lymphoma + nasopharyngeal carcinoma
58
Give the symptoms of Cytomegalovirus
- Causes CNS infections = hearing loss + encephalitis
59
Give the symptoms of ebola virus
- Causes haemorrhagic fever = fatal
60
Describe HPV
- Symptoms = cervical cancer + genital warts - Transmission = sexually - Prevention: > Vaccination > Pap test
61
Describe the prevention measures of HPV
1) Vaccination = Gardasil + Cervarix 2) Pap smear = detect morphological abnormalities
62
Describe poliovirus
- Symptoms = poliomyelitis - Prevention = Sabin/Salk vaccine
63
Describe MMR
- Symptoms = mumps + measles + rubella - Prevention = MMR vaccine
64
Describe Hepatitis
- Liver inflammation - 7 viruses cause = Hep A-G FORMS: 1) Acute = jaundice 2) Chronic = liver cirrhosis + hepatocellular carcinoma TYPES: - Hepatitis A virus - Hepatitis B virus - Hepatitis C virus
65
Describe HAV
- RNA virus - Transmission = food borne - Prevention = vaccine
66
Describe HBV
- DNA virus - Transmission = blood + fluids + sexually - Prevention = vaccine
67
Describe HCV
- RNA virus - Transmission = blood + sexually - Prevention = no vaccine yet
68
Describe HIV
- Discovered in 1981 > isolated 1983 - Infects T-helper lymphocytes - Glycoproteins gp120 + CD4 receptor - Types = HIV-1/HIV-2 - Causes AIDS
69
How is HIV transmitted?
- Sexually = fluids - Blood = needles/transfusion - Mother > child = pregnancy/birth/breast feeding
70
Explain HIV diagnosis
- Detection = in blood 3-6 weeks after infection date - Window period = virus cannot be detected yet = low levels in blood BUT can be transmitted METHODS: - Detect anti-HIV antibodies in blood using ELISA = 6-8 weeks post - Detect viral RNA in blood using RT-PCR = 3 weeks post
71
Describe AIDS
- Infection rate = 6 million people/year - Develops 10-15 years after HIV - Carriers can be asymptomatic + transmit - Anti-retroviral therapy increases life expectancy = 5-20 years
72
What is the T-cell blood count for onset AIDS?
< 200 Th cells/mm3 of blood
73
Give symptoms of AIDS
OPPORTUNISTIC INFECTIONS: - Candidiasis + toxoplasmosis + pneumonia MALIGNANT TUMORS: - Kaposi sarcoma = endothelial cell of blood vessels - Burkitt's lymphoma = B-cell cancer
74
Describe treatment for HIV/AIDS
- No cure + no vaccine due to high mutation rate - HAART = combo of different anti-retroviral drugs - Promblem with anti-retroviral therapy = toxicity + resistance
75
Give the types of anti-retrovirals for AIDS
1) Nucleotide analogues: inhibit viral RNA replication = incorporated into cDNA chain 2) Non-nucleotide analogues: inhibit activity of reverse transcriptase 3) Protease inhibitors: inhibit HIV protease = responsible for viral polypeptide cleavage = maturation of viral particles
76
Describe HIV polymorphism
- New strains due to high mutation - HIV RNA + reverse trasncriptase > HIV cDNA - Reverse transcriptase = 1 mutation per HIV genome PER replicative cycle
77
Give the non-conventional viruses
1) Viroids = without protein capsid - Infectious nucleic acid = replicate in tissue - Plant pathogens 2) Prions = without nucleic acid - Infectious proteins = replicate in tissue - Animal pathogens
78
Describe viroids
- Small + circular RNA - Infect plants = disrupt growth
79
Describe prions
- Slow-acting + indestructible + infectious proteins - Convert normal proteins > prion proteins = aggregation in tissue - CNS infections = spongiform encephalopathies
80
Give examples of prion diseases
1) Mad cow disease = infects cows - Transmitted to humans via contaminated beef ingestion = cooking doesn't kill prions - Causes CJD 2) Creutzfeldt- Jacob disease = infects humans - Fatal CNS infection - Symptoms = ataxia + memory loss + convulsions + coma
81
Describe viral disease in plants
- 2000 known - Cause spots + stunted growth + damage to flower/root - Have RNA genome - E.g. TMV

MED-109 Biology II (10 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions