Chapter 38: Viruses Flashcards
Describe the structure of a virus
non cellular
50x smaller than bacteria
no organelles
have a protien coat (capsid) that surrounds the nucleic acid
What are the two types of nucleic acid?
RNA
DNA
What makes a virus living?
possess genetic material
possess a protein coat
can replicate
What makes a virus non-living?
non cellular
cannot reprouduce themselves
no organelles
only one type of nucleic acid
Viruses are obligate parasite, what does this mean?
they need a living host to survive
What are the 5 stages of replication?
attachment entry synthesis assembly release
Explain attachment.
virus attaches to host cell
proteins on virus line up with receptors on host cell
Explain entry.
hole formed and viral nucleic acid enters
Explain synthesis.
host DNA made inactive
viral nucleic acid uses organelles to produce new nucleic acid and proteins
Explain assembly.
new viruses are made using new molecules
Explain release.
host cell bursts (lysis)
What is lysis?
when the host cell bursts due to a virus formed inside it
Explain how variation in human cells occurs due to a virus.
some viruses dont destroy a hosts DNA but join it
What are the advantages of a virus?
genetic engineering - viruses used to transfer genes from one organism to another
control of infections - bacteriophages used to control bacterial infections resistant to antibiotics
What are the disadvanges of viruses?
disease
plants - tobacco/tomato/potato mosaic disease
human - colds, flues, aids
animal - foot and mouth, cowpox, rabies
What does aids stand for?
Acquired immune deficiency syndrome
What does hiv stand for?
Human immunodeficiency virus
How is aids transmitted?
Enters via bodily fluids e.g. blood, semen Through shared needles, sexual intercourse
What are the effects of aids?
Enters wbc
Can remain dormant or disable wbc (helper t-cells)
What is the effect of aids disabling helper t-cells?
Prevents the person from producing antibodies
Unable to fight off infection
How can aids be controlled?
No cure
Prevents by avoiding sexual intercourse or use a condom
Don’t share needles, toothbrushes, razors, donate blood,semen or body organs
What is interferon?
A substance produced by virus infected cells to protect healthy cells
How can immunity be controlled?
Defence System in the Body Vaccinations Antibody injections Antiviral drugs Acyclovir - treats herpes AZT - slows the development of aids
