Chapter 13- Viruses and Prions Flashcards
When a virus particle is located _______ (outside a cell) it is comprised of 2 basic components: a protein coat called a _____ which surrounds a ______ _____ core. There may be a third component, a phospholipid membrane called an ______, surrounding the capsid.
When a virus particle is located extracellularly (outside a cell) it is comprised of 2 basic components: a protein coat called a CAPSID which surrounds a nucleic acid core. There may be a third component, a phospholipid membrane called an ENVELOPE, surrounding the capsid.
Capsid
A protein coat
Envelope
a phospholipid membrane that surrounds the capsid (only some viruses have them)
The _____ ____ core contains the genetic material of the virus. This can be either _____ __ ____ (part of the _________ structure)
The nucleic acid core contains the genetic material of the virus. This can be either DNA or RNA (part of the intracellular structure)
The capsid is composed of protein subunits called ______. The capsomeres are arranged in different ways creating three basic viral shapes. These are:
The capsid is composed of protein subunits called CAPSOMERES. The capsomeres are arranged in different ways creating three basic viral shapes. These are:
- Helical
- Polyhedral
- Complex
Virus characteristics:
- _____
- no ____ _____, no _______, no ______
- cannot carry out any ____ _____
- neither grow nor respond to ______
- cannot _____ _____
- acellular
- no cell membrane, no cytoplasm, no organelles
- cannot carry out any metabolic pathways
- neither grow nor responds to environment
- cannot reproduce independently
Genetic material of viruses:
- May be DNA or RNA but ___ ___
- Can be ____, _____, ____, or ____
- May be _____ or _____
- Much smaller than genomes of cells
- Composed of same nucleotides as cells (A,T,C,G,U)
- May be DNA or RNA but never both
- Can be dsDNA, ssDNA, dsRNA, or ssRNA
- May be linear or circular
- Much smaller than genomes of cells
- Composed of same nucleotides as cells (A,T,C,G,U)
The viral envelope is acquired from____ ____ during _____ _____ and ____ and is called _____
The viral envelope is acquired from host cell during viral replication and release and is called budding
If an envelope is present it is composed of a _____ _____ and is located exterior to the capsid. The membrane is obtained from the host cell which it infects and ultimately helps in attachment as well as helps in evading the immune response of the host. The main disadvantage to a virus having an envelope is that it is susceptible to detergents, alcohol, and desiccation. Basically, enveloped viruses are ____ ____ than ____ ____.
If an envelope is present it is composed of a phospholipid bilayer and is located exterior to the capsid. The membrane is obtained from the host cell which it infects and ultimately helps in attachment as well as helps in evading the immune response of the host. The main disadvantage to a virus having an envelope is that it is susceptible to detergents, alcohol, and desiccation. Basically, enveloped viruses are more fragile than naked viruses.
The capsid proteins or ______ within the envelope have _____ for not only the species they will attack but more directly, the _____ ____ in the body that they will attach to and infect. Entry of the virus into animal cells then occurs via one of 3 ways:
1.
2.
3.
The capsid proteins or glycoproteins within the envelope have specificity for not only the species they will attack but more directly, the specific cells in the body that they will attach to and infect. Entry of the virus into animal cells then occurs via one of 3 ways:
1. Direct penetration through cell membrane
2. Fusion of cell membrane
3. Endocytosis
Most viruses infect a
specific species
General pattern of a typical virus life cycle:
- Attachment
- Entry of nucleic acids/enzymes
- Synthesis of new nucleic acids and capsids
- Assembly
- Release
The general pattern is called ____ _____
Lytic replication
In many viruses, lysis doesn’t always occur. Instead, newly assembled viruses can be released via _____
exocytosis
Naked vs Enveloped virus
Naked virus is nucleic material surrounded by a protein molecule
Enveloped virus is nucleic material surrounded by a protein molecule, surrounded by a cell membrane
What primarily happens with naked viruses? ____. The same process happens with envelopes, but what differs is..
What primarily happens with naked viruses? lysis
What differs is mode of entry (could do membrane fusion or endocytosis, and when it exits, it doesn’t have to lysis the cell. It can just push its way out and take some of the cell membrane with it.)
Some viruses, once intracellular, go into a period of ____ where they remain ____ only to surface at a later date.
Some viruses, once intracellular, go into a period of LATENCY where they remain DORMANT only to surface at a later date.
Where does the life cycle get altered with latency?
A pause occurs between entry and synthesis
1. Attaches
2. Enters
3. Pauses
4. Synsthesis
5. Assembly
6. Release
Latency is often represented by the ______ _____
Lysogenic replication
Most antivirals are not broad spectrum but rather are ______ to the ____ that’s causing disease in the individual. Most antivirals do not actually kill the virus but instead ____ the replication. Since the virus uses the host cell, it is difficult to develop antivirals that will specifically target the virus without _____ ____ to the ____ ____. Basically, ______ ____ doesn’t apply to viruses because it’s guaranteed to harm the host. The vast majority of the time, the virus is eventually eliminated by a functioning immune system.
Most antivirals are not broad spectrum but rather are specific to the virus that’s causing disease in the individual. Most antivirals do not actually kill the virus but instead inhibit the replication. Since the virus uses the host cell it is difficult to develop antivirals that will specifically target the virus without risking harm to the human host. Basically, selective toxicity doesn’t apply to viruses because it’s guaranteed to harm the host. The vast majority of the time, the virus is eventually eliminated by a functioning immune system.
What is the significance of glycoproteins?
Recognition and attachment
Prions are a _______ agent and are considered _____ ____ that cause neurologic lesions in ____ ____
Prions are a proteinaceous agent and are considered infectious proteins that cause neurologic lesions in multiple species
Example of prion diseases
BSE
scrapie
CWD
kuru
vCJD
Prions:
- ___ _______
- Can only be destroyed by ______
- Cause for disease development:
- Any pattern to age?
- Any pattern to symptoms?
- No treatment
- Can only be destroyed by incineration
- Cause for disease development: inheritance or ingestion
- Any pattern to age? age-related, 50
- Any pattern to symptoms? amyloid plaques/ death
Cellular PrP
Normal protein that has an alpha-helices structure
Prion PrP
Disease-causing form that has beta-pleated sheets
The prion converts normal ___ cellular PrP into __ (bad). Ultimately, prions ____ _____
The prion converts normal alpha cellular PrP into beta (bad). Ultimately, prions don’t replicate
T/F- Prions replicate very slowly
False, they don’t replicate!
