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MIMG wk4 Discussion

Terms in this set (10)

common feature of all viruses
capsid made of protein, nucleic acid genome
differences between viruses
DNA or RNA (single or double), surrounding envelope, different glycoproteins
why are viruses considered parasites?
viruses are intracellular obligate parasites; they enter and hijack the host cell machinery to replicate; they are not able to replicate or metabolize without the host cell. because the abilities to reproduce and metabolize on their own is a major property of all living things, and viruses are unable to do so without the host cell, they are therefore classified as non-living
why is viral attachment to the host cell specific between one virus and one type of cell?
viral attachment is specific due to the type of glycoprotein on the viral surface that specifically binds a host cell receptor on the target cell
three ways a virus enters a host cell
- virus binds to the host cell membrane and injects its genome
- virus bonds to the host cell and fuses its viral protein coat to the host cell membrane in order to transfer its genome
- virus binds to the host cell membrane and it internalized by the host cell (endocytic pathway)
describe the essential cell "machinery" that viruses use to make a new virus
the virus uses enzymes in the nucleus (such as DNA polymerase and DNA helices) for transcription and the ribosomes, tRNA, Golgi apparatus, rER to make proteins and copies of viral RNA/DNA which will be assembled into new viruses particles
why do viruses need the machinery to make more viruses? why can't they replicate on their own?
viruses nee the host cell machinery because they do not contain these enzymes and organelles for synthesis and assembly of new viruses particles
what are the structures that need to be put together during viral assembly? consider the key structural components of viruses
the key viral structures to be assembles are the glycoproteins, genome (RNA/DNA), and capsid proteins. additionally, certain viral enzymes may be packages within the particle as well
how does the army of new viruses get out of the cell to infect the nearby cells
- some viruses with envelopes bud from the host cell, taking pieces of the host cell membrane with incorporated viral proteins
- others leave by exocytosis in vesicles that bud from the endoplasmic reticule or golgi
- viruses without envelopes lyse or break open the host cell and leave that way, often killing the cell in the process
virus replication
attachment - entry - synthesis (replication, transcription, translation) - assembly - release/exit/budding
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