D5: Antiviral medication Flashcards
Explain why viruses are parasites
Viruses invade host cells and use the materials/processes within the cell to replicate and produce new viruses
(since viruses cannot reproduce outside of the host cell)
Describe the structure of a virus
- Core containing genetic material (DNA/RNA)
- Capsid (protein casing protecting core): consists of capsomers (protein subunit)
- Nucleocapsid: core + caspid
- Lipid envelope: protect the nucleocapsid
Distinguish between viruses and bacteria
- Non-living (cannot grow/feed/excrete) vs Living
- Does not contain cellular structure vs Contains cellular structure (Eg. nucleus/cell wall)
- Needs host cell to reproduce vs Can reproduce independently
Explain why antiviral medication is harder to design compared to antibiotics
Lack of cellular structure in viruses means that there are fewer enzymes/receptors for antiviral medications to target
- Vs. Antibiotics: Antibiotics can target the enzymes used to make cell walls
(whereas viruses mostly use the enzymes in the host cell and do not have cell walls)
State the stages of virus replication
1) Attach to the surface of the host cell
2) Release genetic material into the cytoplasm of the host cell and incorporate its viral DNA into host cell DNA
3) Host cell produces new viral proteins and DNA to assemble new functional viruses
4) New viruses exit the host cell and infect other cells
Explain why effective prevention and treatment methods for viruses are hard to find
- Viruses replicate rapidly and can spread to the rest of the body by symptom onset
- Viruses mutate their DNA/RNA quickly, resulting in changes to viral structure and making them resistant to antivirals
- Drugs are likely to affect host cell too (since viruses are parasites)
Explain how the mode of action of viral vaccines and drugs
VACCINES: stimulate the immune system into producing viral antibodies that fight off future infections
ANTIVIRAL DRUGS:
- Alter the genetic material within cells (drug is converted into active metabolite in the cell and is incorporated into the growing viral DNA strand needed for replication, preventing it from being synthesised)
- Inhibiting enzyme activity: enzymes needed for viral replication are inhibited
- Preventing viruses from binding to the surface of host cells
- Prevent viruses from leaving the host cell to infect other cells (Eg. Oseltamivir and Zanamivir)
Describe the structure of the influenza virus
- Genetic information: RNA
- Capsid: RNA and RNA polymerase (enzyme used to make viral proteins and RNA)
- Lipid envelope: contains proteins sticking out of the membrane surrounding the virus
1) Hemagglutin (HA): allow viruses to bind to the sialic acid residues on glycoproteins found on host cell surfaces
2) Neuraminidase (NA): Hydrolyses the bond between sialic acid residues and viruses by acting on sialic acid, breaking the bond and allowing viruses to leave the cell by budding
Explain how Oseltamivir (Tamiflu) and Zanamivir (Relenza) work
Neuraminidase (NA) inhibitors:
Bind to the NA enzyme active site, preventing it from catalysing the hydrolysis of the sialic acid residues and the glycoproteins, so that the drugs remain anchored to the cell and cannot leave it to infect other cells
Compare and contrast the structures of Oseltamivir and Zanamivir
COMPARE (structural similarities allowing both drugs to bind to the same NA enzyme active site):
- 6-membered ring containing alkenyl
- Ester/carboxyl group
(ester group in Oseltamivir is inactive, and is hydrolysed to carboxyl in the body)
- Ether group
- Primary amine group
CONTRAST:
- Zanamivir contains hydroxyl groups
(makes it more soluble in water)
- Zanamivir contains imine group
(makes it highly polar, unable to pass through cellular membranes and unable to be administered orally)
Explain how the HIV/AIDS reterovirus works
Attacks T-cells (white blood cells forming part of immune system):
1) Viruses attach to specific receptor proteins on T-cell surfaces
2) Reverse transcriptase (viral enzyme) converts viral RNA into DNA that is incorporated into T-cell DNA
3) Viral proteins and RNA are produced and assembled into new HIV viruses
4) T-cell membranes form an envelope around HIV viruses as they exit the host cell
State the effects of the HIV/AIDS virus
Weakened immune system:
- T-cells stop carrying out their immune cell functions and become factories to produce HIV viruses
- T-cell death and decrease in T-cell number occurs when HIV viruses exit the cell
Explain why it is difficult to design HIV/AIDS antivirals
- Rapid replication and mutation
- Ability to lie dormant and go undetected
- Use of many T-cell materials/processes to replicate
Explain how HIV antivirals work
Target enzymes used in viral replication process that are not found in host T-cell:
- Eg. Azidothymidine (AZT): inhibits reverse transcriptase (so that viral RNA cannot be converted into DNA to be incorporated into T-cell DNA
- Eg. Inhibits integrase: viral DNA cannot be integrated into T-cell DNA
- Eg. Inhibits protease: viral proteins that produce new viruses cannot be produced
