Lecture #9 Flashcards
1
Q
Are viruses considered cells?
A
No because they have no internal cellular structures
2
Q
What do viruses need in order to multiply?
A
Host cells as they are not free living
3
Q
What do viruses do to a host cell?
A
Use host metabolic systems and usually disrupt normal host cell function
4
Q
What does it mean for a virus to be an obligate intracellular parasite?
A
They do not reproduce outside, rather intracellular
5
Q
What are viruses acellular?
A
They do not have a plasma membrane
6
Q
What are viruses surrounded by?
A
A protein called a capsid
7
Q
Do viruses contain DNA or RNA?
A
They contain a single type of nucleic acid. Can be RNA or DNA but never both
8
Q
Do viruses have their own enzymes?
A
Very few, instead they take over the host enzymes
9
Q
Do all viruses have a lipid envelope and or proteins?
A
No not all
10
Q
What 5 things can viruses infect?
A
Animals, plants, fungi, bacteria and protozoa
11
Q
Most viruses are specific for ______
A
A single host species
12
Q
What must the virus recognize in order to infect a cell?
A
Particular features on the host cell surface
13
Q
What does the HIV virus recognize in order to infect a human immune cell?
A
A specific receptors CO4
14
Q
What microscope are you able to see viruses?
A
Electron
15
Q
How long do viruses range in?
A
20-1000 nm
16
Q
What type of genetic material is found in viruses?
A
Either RNA or DNA, not both
17
Q
Can the genetic material in viruses be single or double stranded?
A
Both can be: dsDNA, ssDNA, dsRNA, or ssRNA
18
Q
What 3 shapes can the nucleic acids of viruses be?
A
- Linear
- Circular (two ends connect)
- Segmented
19
Q
What does it mean when a nucleic acid is segmented?
A
Arranged in many pieces
20
Q
Why is segmented nucleic acids useful?
A
To make more of certain kinds of gene without having to make thousands of unnecessary genes ( don’t have to copy every single other gene not needed)
21
Q
How many nucleic acids are there in a virus?
A
A few thousand- 250000 base pairs
22
Q
How many base pairs does E.coli chromosome have?
A
4000000
23
Q
What is the bare minimum thing you will find on a virus?
A
A capsid
24
Q
What is a capsid?
A
A protein coat surrounding the nucleic acid
25
What is a capsomere?
Individual proteins that make up a capsid
26
What is a capsid made up of?
Capsomeres
27
What does a capsid do for a virus?
Provides the virus with its shape
28
How are capsomeres arranged on a virus?
As characteristic of a particular virus
29
What is a nucleocapsid? What is it in regards to a virus?
A nucleic acid and a capsid together
| This is the minimal required structure for a virus
30
Are envelopes found on all viruses?
No
31
What is an envelope made up of? Where from?
A lipid bilayer (membrane) acquired from host cell
32
Where is the envelope located on a virus when present?
External coating around the nucleocapsid
33
What are spikes? Do all viruses have them?
Additional viral protein inserted into envelope
| No
34
When a virus is enveloped, where is the spikes attached to? What about when it is naked?
Enveloped- attached to envelope
| Naked- attached directly to capsid
35
What is the shape of a virus based on?
Capsid shape
36
What are the 3 shapes of viruses?
1. Helical
2. Polyhedral
3. Enveloped
37
What does a helical virus look like? Describe
Long rod
| Rigid and flexible
38
What does a icosahedral virus look like?
Icosahedral (20 triangular faces)
| Other geometric shapes are possible
39
What shape are enveloped viruses? What dictates the shape?
Roughly spherical, dictated by lipid bilayer
40
What structure do complex viruses have?
Complicated structures
41
What may be attached to the capsid of a complex virus?
Additional protein structures
42
Complex viruses are most common in....?
Bacteriophages
43
Classification of viruses are based one what 3 things?
1. Nucleic acid type
2. Capsid structure
3. Envelope presence
44
What 3 things are considered when classifying virus nucleic acid type?
1. DNA or RNA
2. Single or double stranded
3. Segmented chromosome or single molecule
45
What are two types of capsid structures that are considered when classifying a virus?
1. Polyhedral
| 2. Helical
46
If a virus ends with a viridae, what is it part of?
A family
47
If a virus ends with the suffix virus, it is part of a...?
Genus
48
If a virus is part of a species, how is the species specified?
The virus is given a descriptive name
49
Give examples of a virus genus, family and species
Family: Retroviridae
Genus: Lentivirus
Species: Human Immunodeficiency Virus (HIV)
50
What are the 6 steps of virus multiplication?
1. Adsorption
2. Penetration
3. Uncoating
4. Biosynthesis
5. Maturation and Assembly
6. Release
51
What occurs during adsorption?
Virus attaches to host cell at protein or glycoprotein attachment sites within the host membrane that the virus recognizes
52
What occurs during penetration?
Virus enters.
Naked viruses enter via endocytosis
Some enveloped enter via fusion of lipid bilayers
53
What occurs during uncoating?
Separation of viral nucleic acid from the capsid (opening the lid)
54
During biosynthesis, what occurs?
Viral nucleic acid is replicated
55
Where does DNA vs RNA replication occur during biosynthesis?
RNA- host cytoplasm
| DNA- nucleus of host cell
56
Where are viral proteins synthesized during biosynthesis? What is constructed at the same time?
in the cytoplasm, capsomeres constructed
57
If an RNA virus is taking over a host cell, what needs to happen in order to make RNA from RNA?
an RNA enzyme needs to be brought into the host cell
58
What occurs during maturation and assembly of animal virus replication?
New virus particles are assembles from nucleic acids and capsomers forming nucleocapsids
59
What is the difference in release between enveloped and non enveloped cells?
Naked- burst from cell destroying it
Enveloped- bud out of the host cell causing steady release of mature enveloped viruses over time and host cell remains alive longer
60
What does the host defence do?
Protects against lethal infections
61
Do healthy humans carry both viruses and antibodies for viruses?
Yes
62
If a virus is transferred from the immune host to another individual, what can result?
In infection
63
What are 5 types of infections?
1. Acute infections
2. Acute infections with late complication
3. Persistant viral infections
4. Latent Viral Infections
5. Chronic Viral Infection
64
How long do acute infections last?
Very short duration
65
The symptoms from acute infections can cause?
Tissue Damage
66
How does the host defence system eliminate the infection?
Gradually, from days to months
67
Does the host always develop long lasting immunity after an acute virus?
It can or cannot e.g.. measles or polio
68
How does a acute infection with late complications occur?
Following an acute infection, some particles still last which over time multiply and can cause a serious disease years later
69
What is an example of an acute infection with late complications?
Measles can turn into subacute sclerosing panencephalitis
70
What is a persistent viral infection?
An infection that is present at all times
71
With a persistent viral infection, is the disease always present?
NO
72
What is an example of a persistent viral infection?
Hepatitis B
73
How is Hepatitis B transmitted? What are acute symptoms? What are long term symptoms?
Transmitted sexually or via blood
Acute: Fever, nausea and jaundice
Longterm: cirrhosis or cancer of the liver
74
The infected host of a persistent viral infection serves as a...?
Reservoir
75
What are latent viral infections?
An acute infection followed by an asymptomatic (different symptoms) period
76
What does the virus do in a latent viral infection?
Virus inserts a copy of DNA into the host cell chromosome called a provirus (just sits there, doesn't do anything)
77
Can a latent virus infection be reactivated years later?
Yes
78
What is an example of a latent virus infection? What family does it belong to?
Varicella Zoster Virus, belongs to herpes family
79
What is the varicella zoster virus present early on as? Later on?
Early: chicken pox in children
Later: Shingles
80
What is a chronic viral infection?
After an acute infection, infectious virus remains present at all times (may or may not have noticeable symptoms)
81
What is an example of a chronic viral infection?
Hepatitis B (serum hepatitis virus)
82
Viral DNA can transform normal animal cells into what?
malignant cancer cells
83
Do all viruses have the capability to transform cells into cancer cells?
No only some
84
What are photo-oncogenes?
Animal cells with normal genes
85
What are photo-oncogenes required for?
to stimulate normal cell growth
86
What do tutor suppressor cells do to cells?
Inhibit growth
87
When mutations occur in photo-oncogenes, what does it result in?
Uncontrolled cell growth which then leads to tumor formation and cancer
88
How can mutated genes form?
As a result of mutagens (carcinogens)
89
What are oncogenic viruses?
Carry oncogenes which interfere with cell control mechanisms
90
If oncogenes are present in viral DNA, what could be caused?
Proto-Oncogenes to be over expressed leading to increased transcription causing the proto-oncogne to become oncogene
91
What are 3 possible oncogenic viruses?
1. Human Papilloma Virus
2. Epstein- Barr Virus
3. Hepatitis B Virus
92
How is the Human Papilloma Virus transmitted? What does it cause?
Sexually transmitted causing genital warts
93
Which oncogenic virus is thought to cause cervical cancer?
Human Papilloma Virus
94
How is the Epstein- Barr Virus transmitted?
Transmitted by sneezing
| Can be caused by stress
95
What does the epstein- Barr virus cause?
Mononucleosis which may cause lymphoma and cancers in the nose and throat
96
Which virus is thought to cause almost all cases of liver cancer?
Hepatitis B and C
97
What is a virod?
A single piece of naked RNA with no protein coat
98
What does a virod result in?
Some plant diseases, not yet found in animals
99
What are prions?
Infectious protein particles (turned from good to bad)
100
Is there genetic material (DNA or RNA) present in prions?
No
101
What are prions linked to cause?
Several fatal human and animals diseases
| - ex. Transmissible Spongiform Ecephalophathy
102
Why do prions cause FATAL human diseases? (what does it do)
Because it forms spongelike holes in brain tissue causing brain function to degenerate and neurons die
103
How are prions transmitted?
Most frequently by food?
104
How are prions transmitted to humans?
1. Sheep is infected with prion (scrapie)
2. Infected sheep eaten by cows and cow develops mad cow disease
3. Cow is eaten by humans and develops Creutzfeldt- Jakob Disease
105
What are 4 reasons prions are so resistant?
1. Not usually destroyed by high temps (only by autoclaving but then food is inedible
2. Onset of disease occurs several years after infection
106
Does prions disease always kill you? Is there a cure?
Yes, no
107
How does a single protein become infectious?
A known protein (with an unknown function), gets converted into a prion protein shape. Eventually all np's become pp and this results in disease
