Viruses Part 1 Flashcards
What type of cells can viruses infect? (4)
Bacteria, fungi, plants & animals
( any kind of cell really )
What are viruses?
Obligate intracellular parasites
Are viruses made of cells? And why?
No, they are obligate intracellular parasites
What does it mean that a viruses is obligate intracellular parasites?
Viruses can not replicate outside of a host
( they must be inside a host in order to replicate )
Are viruses acellular?why?
Yes, because they are not made of cells
Are viruses made of cells ?
No
Are viruses living? And why?
Yes they are living as long as they are inside a host, however if they are not inside a host they are not, since they don’t replicate outside of one
Are viruses acellular and living? ( when inside a host )
Yes
Are viruses small ? ( and what is the size)
Yes, 0.3um
Are viruses filterable? Why?
Yes because they are very small
How can we filter viruses?
Using regular filter paper
Do all viruses contain nucleic acids?
Yes
What is the nucleic acid for viruses?
Either DNA or RNA
( NEVER BOTH )
Can there be both, dna and rna, nucleic acids for viruses?
No
What are nucleic acid surrounded by?
Protein coat
( named capsid )^
If viruses have dna nucleic acid, what do we call them?
Dna viruses
If viruses have rna nucleic acid, what do we call them?
Rna viruses
What is considered to be the first step of classification of viruses ?
Whether they are DNA viruses or RNA viruses
What makes DNA and RNA nucleic acids in viruses so speical? (3)
- DNA can be single stranded or double
- RNA can be double stranded or single
- viruses only have 1 type, either dna or rna
Nucleic acid are surrounded by a protein called ?
Capsid
Since the nucleic acid is surrounded by a protein, what else does it mean? ( proteins are ?)
Proteins are made from amino acids
What makes a capsid? ( be more in depth, what covers the entire thing of it? Units ?)
Capsomere
are the units to make a capsid^
(So obviously proteins ( amino acids ))
Do all viruses have a capsid?
Yes
Why does a viruses need to use a host in order to replicate?
Viruses don’t have any ribosomes to make proteins
&
Have very few enzymes for replication so they will need to go into a host to use THEIR enzymes for replication and packaging
Some viruses but not all viruses will have a what to a protein coat? ( capsid)
An extra layer surrounding the protein coat
What is this extra layer that surrounds the protein coat ( capsid) called?
Envelopes
What are envelopes made of?
Phospholipids (lipids)
Capsid are made of ___ & envelopes are made of ___?
- Proteins
- Lipids ( phospholipids)
Where do we usually find phospholipids? ( in bacteria )
Cell membranes
Viruses that have an envelope are called?
Envelope viruses
Viruses that don’t have an envelope are called?
Naked viruses
Or
Non envelope viruses
If viruses have an extra layer, the envelope, why are they easier to destroy?
Because anything with lipids, it’s much easier to destroy than proteins
Lipids envelopes are susceptible to?
Disinfectants
Why can’t you treat viral infection with antibiotics?
Becauses viruses aren’t sensitive to it
( some story behind this )
The reason why we have a trouble with antibiotic resistance is because of this.
We would never, in the past, look if it was a virus or bacteria, so most things just gain resistance since how much we used it on them
Are viruses smaller than bacteria? Typically?
Yes
Why are viruses not considered cells?
Because they don’t have ribosomes
&
They can’t keep themselves in a stable state to grow or make own energy
What is a complete infectious particle?
Virion
What is a virion?
Complete infectious particle
What is a virion made of? (3)
Nucleic acid surrounded with capsid and no envelope
Or
Nucleic acid surrounded with capsid with envelope
Envelopes virus need their envelopes in order to infect others? Why?
Yes, the only reason why envelopes viruses infect is because of that envelope; without it is isn’t comeplete
What is the genome for viruses?
Contain a single type of nucleic acid
( dna or rna ) NEVER BOTH
How many genes in a genome viruses?
Varies, though few genes to 250 genes
What are the 3 steps to classification of a viruses?
- Based on nucleic acid content
(DNA or RNA ) ( single or double ) - Capsid ( structure geometric )
- Envelope ( have it or not )
For nucleic acid, classification section, what can they be?
Dna can be single stranded
Rna can be double stranded
Dna or Rna, never both
Single stranded RNA viruses, what can we divide them into?
Positive sense RNA viruses or Negative sense RNA viruses
Is the negative and or positive rna sense viruses only for Single stranded rna ?
YES!! ONLY
What are single stranded positive sense rna viruses?
Can act like a messenger RNA when it infects the cell
What are single stranded negative sense rna viruses?
When it enters the cell, it just first be copied into a complentary strand, that is the mRNA
Then the translation of proteins can start occurring
To summarize, what is the only expection to where we can divide the nucleic acid into 2 groups?
Single stranded RNA viruses
To summarize, what are the 2 groups the SS rna divide into?
Positive sense rna virus
Negative sense rna virus
To summarize how do you differentiate between the positive and negative sense viruses for SS rna ?
Positive
- can go into the cell and function like an mRNA
negative
- has to first get a complentary strand
( transcribed into a RNA strand )
In order for it to serve as a mRNA
Do all viruses have a capsid?
Yes
What is a capsid?
A protein coat surrounding the nucleic acid
What does each capsid have that is composed of units?
Capsomers
Depending on the capsid shape, what do we call it?
Symmetry
What are the 3 symmetry, capsid shape?
Helical, polyhedral, complex
What is helical symmetry? (looks like ?) ( 3 )
Looks like a rod
Many copies of the same protein wrapped in a helix
Nucleic acid surround by hollow cylindrical capsid
What are 2 viruses that fall under helical symmetry?
TMV ( tobacco mosaic virus )
Rabies virus
( Ebola too btw !)
What is a polyhedral symmetry? ( looks like?) (2)
Many sides
Most common shape is
Isosahedral
( 20 sides with 12 corners )
What is the most common polyhedral symmetry and what does it have?
Icosahedral
( 20 sides with 12 corners )
What are the 3 viruses that are icosahedral shapes?
Polio virus
Adenovirus
Herpes virus
What is complex symmetry?
Complicated structure
( variety of shapes )
What is the most common complex symmetry?
Bacteiophages
Bacteriophages shape is complex symmetry but why?
Because it has a capsid ( one shape )
A tail ( another shape )
A sheath ( and another shape )
Too many complex structures
What is a virus that follows under a complex symmetry?
Pox viruses ( small pox )
Do all virus have envelopes?
Nope
What are envelopes made up of?
Phospholipids
What are the spikes on the envelopes viruses called?
Spikes or peplomers
What are the spikes ( peplomers ) function for the envelope viruses?
Glycoproteins
( receptor of the virus to attach to a cell )
Where would the receptors be on a naked virus ?
On the capsid
( the reason why is because envelopes have that extra layer, so the spikes are on the envelopes, where as those who are naked don’t, so you’ll find them on the capsid )
Are virus specific to a type of cell that they infect ?
Yes, very specific
( specific cells )
Why are viruses so specific to a certain cell? When it infects the host?
Because the glycoproteins, that are found on the surface of the virus, spikes, must find the perfect receptor to attach to the cell
( lock & key moment )
How did the lock and key specific receptors come to be for viruses?
Evolution
If a pathogen can not attach to the surface of the cell, it can not ______
If it can not infect that cell,_____
- Not infect that cell
- It cannot cause disease
What is the taxonomy of viruses ?
( how did we use to do it, then better method, to now? ) (3)
First
Classified by host
( animal, plant or bacteriophages )
Then
Classified by disease caused
( respiratory dissease or enteric viruses )
TODAY
Classified according to structure
( nucleic acid type, replication strategy, morphology )
