Why can't viruses replicate on their own?
*They are obligate parasites. They lack ribosomes, amino acids, nucleotides, E.R. or golgi to assemble proteins.
^How do viruses interact with cell surfaces?
*Proteins on their surfaces determine what cellular receptors through which it will enter.
^What are viruses made of?
*Proteins (capsids & enzymes), nucleic acids (RNA or DNA) and sometimes lipid envelopes.
^What is the major viral protein and what is it used for?
*Capsid. Protein coat that surrounds the nucleic acid. These protein coats can self assemble in the rough E.R., initiating virus assembly.
^How are viruses classified?
^Viral protein syntesis
^Why are +ssRNA viruses so infectious?
*DNA/RNA hybrid is incorporation into host DNA and infects the host for life.
^What is the viral membrane made of?
*Mammalian cell membrane. Phospholipids bud off as the virus exits the cell.
^What chemicals are enveloped viruses particularly sensitive to?
*Acids and detergents. They disrupt the phospholipid membrane.
^GI disease viruses
*Non-envelope viruses. They can survive on door-knobs for long periods of time.
^Where do RNA viruses replicate (copy its genome)?
*Cytoplasm. DNA viruses replicate in the nucleus.
^What is an exception to RNA virus replication location?
*HIV. It is replicated in the nucleus and incorporated into the genome because it is a DNA/RNA hybrid.
^What enzymes do most RNA viruses carry?
*RNA-dependent RNA polymerase.
^What enzyme does HIV carry?
*RNA-dependent DNA polymerase. This reverse transcribes RNA to DNA.
^What enzyme do most DNA viruses carry?
*DNA-dependent RNA polymerase
^How do nonenvelope viruses leave the host cell?
^How does the virus get into the cells cytoplasm?
*Penetration by cutting membrane and releasing virus, fusion with membrane and release of virus or endocytosis and degradation to release virus.
^How are envelope viruses released from a host?
*Viral glycoproteins go to the membrane. The membrane closes around the glycoproteins. Enveloped virus exits.
^What various morphological changes can be seen in a virus-infected cell?
*Ballooning, rounding, giant cell formation, inclusion bodies or lysis.
*Misfolded viral proteins that aggregate within the cell. DNA viruses will have inclusion bodies in the nucleus. RNA viruses will have inclusion bodies in the cytoplasm.
*Giant cell formation
*Viruses stop producing proteins and "hibernate".
*The way viruses evolve to preferentially target specific cell types or tissues.
^Where are viral receptors located? What do they receive?
*On the surface of the capsid. They help the virus attach to the host. They determine what cells the virus can infect. Usually each virus can only infect one type of cell.
^What shapes do capsids come it?
*Icosahedral and helical.