✅2: Viruses Flashcards
What are viruses?
They are not made of cells. They’re not considered living, as they don’t display any characteristics except reproduction.
How are viruses classified?
According to their structure and type of nucleic acid that they contain. All viruses either contain DNA or RNA.
What do viruses contain
DNA or RNA. Enzymes such as protease, that are useful for entering cells. Capsid- surrounding thing made of protein. Sometimes lipid membrane that is derived from cell it was formed in.
What are the 4 viruses we need to know
Lamda phage
Ebola
TBV
HIV
What does lambda phage look like
Classic virus, with capsule made of proteins, a base plates and legs” with a head and tail DNA
What does TBV look like
Long with RNA. And capris made or proteins
What does Ebola look like
A work- outer lipid membrane and capsule made of proteins. RNA
What does HIV look like
A sphere, with outer lipid membrane, reverse transcriptase, RNA, and a capsid made of proteins
What is the lytic cycle
attaches to receptor on cell membrane. Only certain cells have receptors to attach. Virus injects DNA or RNA into host cell. Im retroviruses, one of the viruses own enzymes, reverse transcriptase, makes a DNA “copy’ of viral dna
Viral dna uses hosts cells enzymes and ribosomes to make new copies of the viral DNA and protein. Assembled to make new viruses and burst out of cell and destroy it- LYSIS.
What is latency
Some viruses, including HIV, don’t make new viruses immediately, but insert viral DNA into host cell chromosomes where it can lie dormant for years. Eventually the viral DNA is activated and expressed.
Why are viral diseases difficult to treat?
Antibiotics don’t affect viruses. Ebola break out in 2014-15 show this. Where outbreaks are severe, may become ethically justifiable to treat people who would otherwise almost certainly die by use ONG recent Durga which haven’t completed trial
What is virus classification?
They are non cellular, the host cell dues as new viral particles are released surrounded by capsid, and made my repeating proteins subunits called CAPSOMERE. many viruses surrounded by lipid envelope of the body cell
What type of genetic material is in lambda phage?
Double stranded liners DNA.
What is lysogenic pathway.
Lays dormant and starts resident in host genome without apparent harm to the host, lysogen when ohrphage is present. This prophase May enter the lyric cycle when I stressed conditions
What does TMV cause?
Causes patterns and mosaic like mottling and discolouration on the leaves. Damaged the cell walls
How does TMV travel?
Can’t ravel via plasmidesmata and into the phloem.
How does TMV work?
Positive sense RNA and it mimics mRNA and translated at ribosomes. Protein encoded by TMV RNA and included RNA polymerase to manufacture more RNA for inclusion in new capsid
Where abouts does the ebola virus infect?
Infects human cells; the liver cells, cells in the immune system, the endothelial cels etc
What symptoms are from Ebola
Haemorrhaging fear, with a fever, headache, muscle pain and eventually vomiting and diarrhoea . Internal bleeding
How does Ebola distrust cell adhesion and why?
A glycoproteins made my the Ebola virus can disrupt cell adhesion so that cells have trouble sticking together. And to a scaffold called the extra cellular matrix, which in earth tissues helps the cells hold together.
What happens when the Ebola cells cause the humans cells to not stick?
Virus causes vessels to become leak leading to haemorrhaging and internal bleeding.
What is the Ebola structure?
Filamentous, and usually coiled. May be branched. Outermost viral envelope is a lipid belayer which the virus particle pick up from the animal cells.
What is the genetic codes on Ebola?
Single stranded RNA, negative sense
How does the RNA on Ebola work?
Once inside the host cell, viral RNA polymerase catalysed the synthesis of the equivalent of mRNA using the viral RNA as a a template. Therefore the RA formed can be transplanted at the hosts ribosomes.
How does the virus move into the cell?
Binds to receptors on the host cell surface membrane, through its glycoproteins spikes, and causes unfolding of the host membrane. Virus is trap sorted into the cell wrapped in a piece of the membrane.
Virus is then placed into various compartments of the cell, in the attempt to destroy the virus.
Which arts of the cell try to kill the Ebola virus once its inside the cell?
Lysosomes, endoscopes, macropinosomes.
What caused the Iraq membrane to bind with the endosomal membrane?
Series of events allows the fusion of membranes, which releases the virus into the cell.
How is the viral genetic info in Ebola copied?
Viral RNA is released into the cytoplasm. Vial genome (negative sense RNA) is transcribed into mRNA with the aid of RNA polymerase. Then translated into Provis using host cells energy, ribosomes and raw materials.
How are glycoproteins modified in Ebola action?
Further oxidised in the Golgi apparatus, and delivered to the host plasma membrane in secretory vesicles. Therefore the viral glycoproteins are incorporated not the host cells surface membrane
What is HIV and which cells does it affect?
Human immunodeficiency virus. AIDS is the disease caused by it.
Affects the helper T lymphocytes, macrophages and dendritic cells.
Why is HIV classed as a retrovirus?
They have positive sense strands ssRNA as their genetic material. Also capable of manufacturing double stranded DNA using their RNA as a template. This DNA can then be integrated int the host’s genome.
How does HIV enter the cells nucleus?
The viral RNA is converted into double strand DNA by a viral genome in the virus particle. It’s then imported into the nucleus and integrated into the cellular DNA by a virally ceded integrate and how co factors. Once intergrated, the viral DNA is known as a provirus, may be latent for years, allowing its host cell to avoid detection by the immune system.
When does HIV become shown?
Lies dormant for years and replaced with the cell. At an environmental trigger, the viralDNA is transcribed, producing new RNA genomes and viral proteins, including capsomere proteins for new capsids.
Virus particles are released by budding, cop pecking their lipid envelope from the host cell membrane.
What are treatments for viral diseases?
Difficult to treat. Viral reproduction uses host cell enzymes, but there are few viral enzymes that can be targeted by drugs.
Examples of drugs which can treat viruses
AZT: resembles a nucleotide. Competently inhibits the enzyme reverse transcriptase found in retrovirus like HIV
Tamiflu: competitive inhibitor of the viral enzyme neuraminidase that many viruses including the influenza flu, use to escape from cells
How do you control viral diseases?
Difficult to treat, therefore have to deal with the outbreak to four on the spread, rather than the cure.
What’s an epidemic?
When a disease spreads rapidly and unexpectedly to affect manny people.
Eg Ebola outbreak 2014 in west Africa.
What is a pandemic
A disease which affects people over very large areas, such as a continent or even the whole world. AIDS and TB are pandemics.
What are the three stages in preventing a spread on an epidemic?
1: identify the outbreak and respond quickly
2: reduce spread by enforcing simple cultural and hygiene practices
3: impose travel restrictions to and from the region to prevent infection from spreading to other countries
How do you identify the outbreak and respond?
I 2014 Ebola, t took 6 months before the world health organisation coordinated an international response
It has to be quick
How do you reduce the spread by enforcing cultural hygiene’s?
Have to be used by healthcare worker Es, and other people in contact with patients or victims
Hand washing before and after contact
Wearing protective clothing such as face masks, goggles, gowns and gloves
Taking care when handling and disposing of bodily fluids.
Sterilising or disposing of equipment and bedding after use
Nursing in isolation
Cultural practises such as washing the dead have to be stopped
Hw do you impose travel restrictions?
2014 quarantine area was established around a triangular area of Guinea, Liberia and Sierra Leone. 70% of the known cases had been found. No one was allowed to enter or leave to prevent further spread.
What are the ethical implication of using untested drugs during epidemics?
May become ethical justifiable to treat people who would otherwise die, by using recently produced drugs that haven’t yet been through full trial procedure.
Factors to consider when determine whether an untested drug should be used
The severity of the disease
The availability of other treatments
The effectiveness of other measures being taken control the spread of the disease
Informed consent of those who will receive treatment
Effective collection of clinical data from the use of new medicine so its safety an efficacy can be evaluated.
Reasons agains using untested drugs
My cause unexpected deleterious side effects . Could make death worse etc
Decisions have to be made regarding who received treatment if the drug is limited
Would need informed consent, this may be difficult because o the understanding of how the drug works and the potential side effects. I may require a high level of education.
